This post is an attempt to keep track of the terms that differ between dialects of English or exist in some dialects but not others: British / Australian / Canadian / American / etc.

Please note that Canada may be difficult to classify, as some regions (especially near the southern border) use US terms, while others may use UK terms.

It's a community wiki, so feel free to edit and clarify or add additional items. The comments are getting long, so use answers for discussion of specific concepts if necessary. If you're not sure what a term means, ask it as a new question and tag it with language)

Also see What international cooking terms sound similar but have different meanings? for similar issues with other languages.

Fruits & Vegetables:

• Eggplant (US, AU) is an aubergine (UK).
• Zucchini (US, AU) is a courgette (UK) when harvested young or a marrow (UK, AU) when allowed to mature further.
• Summer Squash (US) are members of the squash family with a short storage life typically harvested before full maturity; typically available starting in the spring and summer; includes zucchini, yellow and crookneck squash.
• Winter Squash (US) are members of the squash family that are allowed to reach full maturity before harvesting; typically available in the fall; includes pumpkin, acorn and butternut squash.
• also note that squash may refer to a drink (see "cordial")
• Arugula (US) is rocket (UK, AU).
• Rutabaga (US) is swede (UK, AU), but also called turnip, Swedish turnip or neep in some parts of the UK, particularly Scotland. (Wikipedia)
• Endive (US) is chicory (Belgium, perhaps others).
• Capsicum (AU) / bell pepper (US) is a pepper (UK). Note that for people with a biology background 'capsicum' also includes hot peppers (aka chilies or chili peppers)
• Peppers (US) (note the plural), is typically short for chili peppers unless qualified as sweet peppers or bell peppers, or specified as peppercorn.
• Colored peppers (US), (eg, red peppers, green peppers), typically refers to bell peppers unless qualified (eg, 'hot red peppers', 'small red peppers')
• Pepper (US) (note the singular) refers to black peppercorns unless otherwise qualified.
• Red pepper (US, note the singular) refers to dried, red chilies (typically cayenne) that has been dried and ground or crushed.
• Seaweed (US) has many names based on type of plant, including Kombu (Japan), Nori (Japan), Laver (Wales), and many others. See (edible seaweed)
• Snow peas (US, AU) are mange tout (UK) (word borrowed from French meaning 'eat everything'). Mange tout (UK) also includes sugar snap peas (US).
• Peanuts (US, AU) may sometimes be sold in the UK as monkey nuts, especially if unshelled. And Peanut Oil may be known in the UK as groundnut oil.
• Legumes (US) are pulses (UK). 'Legume' may refer to the plant and not the seeds (lentils, beans, etc).
• Boiling potatoes (US) are waxy potatoes (UK, US). This refers to low-starch potatoes that don't fall apart when cooked. Sometimes called roasting potatoes (US). New potatoes behave like waxy potatoes, even if they come from a variety used for baking.
• Mealy potatoes (US) are floury potatoes (UK) or baking potatoes (UK, US). This refers to high starch, low moisture potatoes that result in significant softening when cooked (useful for mashed potatoes or using for thickening; the opposite of waxy potatoes).
• Runner Beans (UK) are green beans or string beans (US, CA) (Farmhouse Cookery). UK also has green beans and stringless beans, but neither is the same as runner beans.
• Broad Beans (UK, AU) are fava beans, butter beans or lima beans (US, CA) (Farmhouse Cookery)
• Sultanas (UK, AU) are seedless golden raisins (Farmhouse Cookery)
• Spring onions (AK, AU, CA), Scallions (US), and green onions may not always be the same thing, but can typically be substituted for each other. (more details).

Herbs, Spices & Seasonings:

• Kosher(ing) salt (US) is flaked salt (UK). Some sea salts may be appropriate substitutes (ref).
• Cilantro (US) is known as Coriander (UK, AU), and it tends to refer to the leaf, unless qualified as coriander seed. May be qualified as fresh coriander or green coriander. Ground coriander is always the seed.
• Coriander (US) refers to the seed.
• Celeriac (UK, AU, US) is celery root (US) (Farmhouse Cookery)
• Stock cubes (AU) are bouillon cubes (US). May be Maggi cube (UK; brand name issues)
• Mixed Spice (UK) aka pudding spice (UK) is roughly equivalent to Pumpkin Pie Spice (US). Both are spice blends heavy in cinnamon and nutmeg, likely to have allspice and possibly other similar spices. Either one may have ginger and cloves as well. Mixed spice may contain coriander (seed) or caraway.
• Chili powder (US) is a spice mixture for seasoning chili con carne. Chili powder contains mainly ground chili peppers (eg, cayenne), onion powder, garlic powder and cumin. Mixtures vary, and often include oregano, black pepper, paprika and/or salt.
• Chili powder (UK) is pure ground chili peppers. In the US, it is usually qualified with a variety of chili and includes an "e" such as "New Mexico chilie powder" or "Ancho chilie powder". (See also "red pepper", above.)
• (see also 'peppercorns' for a discussion of 'black pepper', under the discussion of 'pepper' in Fruits & Vegetables)

Baked Goods:

• Cookies (US, CA) are biscuits (UK, AU, NZ).
• Biscuits (US, CA) are similar to a scone (UK, AU, NZ), and usually neither sweet nor savory. Note: bisquit (Germany, no plural) is sponge cake (US).
• Graham Crackers (US) are roughly analogous to Digestive biscuits in the UK (both may be used to make a crust or dessert base, for example).
• Muffin (US, AU, NZ) is a quick bread (typically using the 'muffin method') baked in forms used for cupcakes. It increasingly has this meaning in the UK too, with the prevalence of American-style coffee-shop chains. Muffin (UK) is english muffin (US, AU, NZ), a yeast leavened flat-ish bread, cooked on a griddle with a ring form.
• Scone (US, CA) tends to be sweeter than a scone (UK).
• Sponge cake is a term for the lighter range of "typical" cake in both US and UK. However, since the range of cakes typically baked varies between the US and UK, in British usage one finds "sponges" that are heavier and denser than what an American would call a "sponge". See this answer for further discussion.
• Pancake (US, CA) Pikelet (AU, NZ) generally refers to puffy items made from a thick leavened batter but generally smaller than an American pancake. (AU may use 'pancake' for items larger than "silver dollar pancakes"). Pancake can go by a number of names in the US, including hotcakes, griddlecakes, flapjacks and hoecakes.
• Pancake (UK, AU) is made from a thinner unleavened batter, with a result a little thicker than a french crêpe. Drop scone (or scotch pancake) (UK) is similar to a (US, CA) pancake
• Flapjack (US) is the same thing as a (US) pancake. But flapjack (UK) is a baked square usually consisting of sugar/honey, butter, and oats.
• Frosting (US) is icing (UK, CA, AU, NZ). In the US, frosting typically has air whipped into it, while icing (US) doesn't and dries harder.
• Turnover (US) or hand pie (US) is pasty/pastie (ˈpas-tē) (UK, NZ). (Pasties (ˈpās-tēz) in the US are coverings to comply with nudity laws in strip clubs.) Turnover (UK) is a puff pastry shell, usually triangular, filled with fruit and whipped cream. In Australia, pasty is usually a meat and vegetable filled pastry, while a similar fruit-filled items is a turnover
• Flan (US) is créme caramel (AU). (ref)
• Flan (AU) is a sweet pastry tart, usually containing custard and fruit.

Flour:

• plain flour (UK, AU) is all-purpose flour (US) (aka 'AP flour' or just 'AP' on cooking shows) unless otherwise qualified (eg, 'plain, strong flour') in which case it just means 'not self-rising'. Note that AP flour in the US South (eg, White Lily brand) tends to be softer than northern and national brands of AP flour (eg, King Arthur, Gold Medal, Pillsbury).
• soft flour (UK) is lower gluten than AP flour, such as pastry flour (US) or cake flour (US)
• strong flour (UK) aka. hard flour (UK) is higher gluten flour, such as bread flour (US)
• self-rising flour (US) is available in the US, but less common. It is referred to as self-raising flour in the UK, AU and NZ. Although it has baking powder in it, it does not have fat in it such as Bisquick or other 'baking mixes'.
  UK Self-raising flour does not contain salt. Apparently US self-rising flour does.
• wholemeal flour (UK) is whole wheat flour (US)

Meats:

• Ground beef (US) is minced beef (AU, UK) or simply mince (UK, AU, NZ).
• Canadian bacon (US) is also back bacon (from the loin).
• Bacon (CA, US) is streaky bacon (UK) (from the belly). In the UK, bacon is most likely back bacon.
• Green Bacon (UK) is "unsmoked bacon cured in brine" (Farmhouse Cookery)
• Gammon (UK) is "ham-like bacon from the pig's hindquarters" (Farmhouse Cookery)
• Pork rinds (US) are scratchings (UK, when dry) and crackling (AU,NZ & UK when fresh from a roast).
• Brawn (UK) is head cheese (US, CA) (Farmhouse Cookery)
• Names of cuts of meat in the US may differ from other countries. See Wikipedia for images of US and British names of regions
• Prawns (AU, UK) and shrimp (US) are technically different animals, but are frequently labeled by the more common one in that country, and are often substituted for each other.

Dairy: (ref, ref)

• Light Cream (CA) has 5% butterfat. Light Cream (US) is 18 to 30% butterfat. (Lite Cream (AU) is roughly 18% butterfat)

• Table Cream (CA) is 15% or 18% butterfat.

• Single cream (UK) is 18% butterfat. Equivalent to Lite Cream (AU), Thickened Cream – Reduced Fat (AU), Table Cream (CA), Coffee Cream (CA). Extra Thick Single Cream (UK) contains stabilizers.

• Cream (US) with 5% butterfat is Single cream (UK), while cream with 48% butterfat (US) is double cream in the UK.

• Half-and-half (US) is a mix of half cream, half milk (about 12.5% butterfat in the US, but 10% butterfat in CA). May be called blend cream (CA).

• Cooking Cream (CA (Quebec)) is either 15% or 35% butterfat, thickened with stabilizers and emulsifiers

• Country-Style Cream (CA (Quebec)) is either 15% or 35% butterfat, with stabilizers and emulsifiers

• Whipping Cream (CA) is 33 to 35% butterfat, and may have stabilizers. Equivalent to Thickened Cream (AU), Pouring Cream (AU) or Single Cream (AU). Whipping Cream (US) may be from 30 to 36% milkfat.

• Heavy cream (US) aka heavy whipping cream (US) = cream with more than 36% fat, and often has stabilizers

• Regular Cream (AU) or Pure Cream (AU) are roughly 40% butterfat without thickening agents.

• Double Cream (UK) is 48% milkfat. Extra Thick Double Cream (UK) contains stabilizers.

• Rich Cream (AU), Thick Cream (AU), or Double Cream (AU) is a spoonable cream with 48% butterfat or more.

• Clotted Cream (UK) or Devon Cream (UK), has been heated to evaporate liquid, resulting in a spoonable cream with about 55% milkfat.

• Buttermilk (US, modern usage, aka 'cultured buttermilk') is a fermented product, basically a runny yogurt, while historically buttermilk is the liquid left over after churning butter. Historic buttermilk made with fresh milk is closer to today's skim milk, but if made with sour milk is closer to cultured buttermilk.

• Sour cream (US) = soured cream (UK)

Sugar:

• powdered sugar or confectioners sugar (US) is icing sugar (UK, CA, NZ) or icing sugar mixture (AU); contains cornstarch (~3%) as an anti-clumping agent.
• icing sugar (AU), aka pure icing sugar does not have starch in it.
• superfine sugar (US, CA) is caster sugar (UK, NZ, AU); may also be called berry sugar (CA), fruit sugar (CA), bar sugar, castor sugar, instant dissolving sugar, ultrafine sugar, fondant sugar, or extra fine sugar.
• sanding sugar (US) is pearl sugar (CA). (size between coarse sugar & granulated sugar)
• unless otherwise qualified, sugar (US, CA) is granulated sugar

Other Food / Ingredients:

• entree (US) is the main course. Entree (AU, NZ) is a starter course, or appetizer (US) course. (ref)

• dessert (US, AU) is pudding, sweets, dessert or afters (UK, depending on region and social class). Pudding is always a cooked item, while dessert may be fresh fruit or other non-cooked item.

• pudding (US) is roughly equiv. to custard (UK)

• jello (US; brand name issues) is jelly (UK, AU)

• jelly (US) is seedless jam (UK, NZ) (see answer below for details)

• fries (US, abbr. for french fries) are chips (UK, NZ); both terms work in AU, as does hot chips

• chips (UK) are steak fries (US), rather than the typical American shoestring fries

• chips (US, AU, NZ) are crisps (UK)

• cornstarch (US) is cornflour (UK, AU, NZ)

• corn flour (US; aka fine corn meal) is maize flour (AU),
  a finer ground version of cornmeal (US,UK) or polenta (US,UK). Cornflour (UK) is the extracted starch derived from the raw corn kernal, not the dry ground flesh of the whole kernal. Also called masa harina (US) if made from nixtamalized corn.

• cornflour (AU) is a powdered starch, but not necessarily made from corn, as there is also 'wheaten cornflour'. (ref)

• cider (US) is unfiltered (cloudy) juice, commonly from apples, while cider (UK, NZ) is an alcoholic beverage made from apple juice (aka. hard cider (US) or scrumpy (UK) for stronger dry ciders). cider (AU) refers to both the alcoholic beverage and any non-alcoholic carbonated apple juice.

• cordial [US] is a flavored alcohol, while cordial [UK, AU] is a liquid drink flavoring that is intended to be diluted with water. (ref)

• liquid smoke (US) is condensed smoke, used as a flavoring.

• black beer (UK) is a malt liquor/fortified wine containing malt.

• black beer (US, Germany), also called black lager or schwarzbier is a type of lager brewed with extremely dark malt.

• tomato sauce (UK, AU, NZ) is ketchup (UK, US). Also catsup and other spelling variants.

• tomato sauce (UK, US) is a tomato based sauce typically for pasta or pizza.

• marinara (US) is used synonymously with tomato sauce, and may refer to both quick or long-cooked varieties.

• tomato paste (US) is tomato purée (UK), a thick, concentrated tomato product.

• tomato purée (US, AU) is unreduced tomatoes (possibly stewed) with the skin and seeds removed. Also called crushed tomatoes (although crushed tomatoes may still have seeds).

• tomato passata (UK) (sometimes just 'passata') is strained tomato purée (US).

• golden syrup (UK, NZ) is dark cane sugar syrup (US, CA); corn syrup is an acceptable substitute (Farmhouse Cookery)

• rapeseed oil (UK) is Canola oil (US, AU, NZ). (abbreviation for "Canada oil, low acid")

• vegetable oil (US, AU) is any flavorless oil with a decent smoke point. It may be soy, corn, or a blend, but you can use peanut (groundnut (UK)), canola (rapeseed (UK)), or extra light (not extra virgin) olive oil.

• oats (US) unless qualified are 'old fashioned' or 'rolled oats', not groats (which are sold as 'pinhead oats'), 'Steel cut oats' (cut up groats but not flattened, aka. 'Irish oatmeal'), nor 'instant oats' (flattened & parcooked).

• granola (US) is a cooked sweetened oat dish that may include nuts or dried fruit, and may be pressed into bars. It looks similar to muesli (UK) which is raw oats, nuts and fruit.

• trail mix (US) is a mixture of nuts and dried fruit. It may include granola, seeds (eg. sunflower) or chocolate (typically in the form of M&Ms)

• Smarties (UK, AU) are similar to the candy M&Ms

• Smarties (US) are compressed sugar pellets (similar to PEZ tablets, but round with concave sides, packaged in rolls with twisted ends)

• Candy (US) is sweets (UK) or lollies (NZ)

• Fried egg in the UK is what Americans call sunny-side up unless otherwise qualified. The US terms over-easy, over-medium, over-well and over-hard are typically unknown in the UK. For a definition of the 'over' terms, see Can someone please give an explanation of different egg preparations? . (more details )

• Casserole (UK) is a stew, a mixture of bite-sized chunks of (typically) meat and vegetables that is cooked submerged in liquid at low heat for a long period of time.

• Casserole (US) is a bake (UK,US) or hotdish (US), and refers to any mixture of food baked in a casserole dish (sometimes shortened to simply casserole), an oven-safe, relatively deep, typically ceramic vessel. A casserole (US) is typically not as wet as a stew. It includes dishes that are composed of pre-cooked ingredients and then mixed or layered in a suitable vessel and baked to finish. (ref)

Cooking methods:

• broiling (US) is grilling (AU, UK) which is cooking with heat from above as in some ovens or restaurant salamanders.
• grilling (US) is barbecuing (AU, UK) which is cooking with heat from below, typically on a metal rack over a vessel of burning wood or charcoal, or a gas burner.
• barbecuing (US) is slow cooking using wood or charcoal to impart smoke to the food. This sense is also sometimes used in AU.
• barbeque (US) (sometimes abbreviated BBQ) may refer to the either food cooked through barbequeing, or the device on which it is cooked.

Tools / Equipment / Non-food items :

• parchment paper (US, CA) is greaseproof paper (Ireland/ UK, NZ) and baking paper (AU)
• stove (US, CA, AU, NZ) is also range (US, CA) and hob (UK). Hob can refer to both the stove as a whole, or an individual burner (aka. heating element).
• crock pot (US; brand name issues) is a slow cooker (US, UK, AU). Also slo-cooker (UK; brand name issues)
• food processor (US, CA, AU) is sometimes a magimix (UK; brand name issues)
• canned items (US) are tinned (UK, AU). Items 'canned' in glass jars would be described as either preserved or pickled (if in vinegar) in the UK.
• recipe (US) is sometimes called a receipt in other areas and in older usage (until early 20th century; more info).
• receipt (US, modern usage) is "a written acknowledgment of having received a specified amount of money, goods, etc."
• aluminum foil (US), aluminium foil (UK, AU) is often referred to as tinfoil (US, UK, NZ), which had previously been in use for similar purposes. It is usually shortened to foil or al-foil in AU.
• plastic wrap (US), cling film (UK), cling wrap (AU) is often referred to as Saran™ wrap (US brand name) or Glad™ wrap (NZ, AU brand name) (although no one bothers to say the '™')
• liquidiser (UK) is a blender (US, CA) (Farmhouse Cookery). blender in AU refers to both a food processor and a liquidiser.
• skillet (US) is a frying pan (US, UK, NZ). (a type of low-sided round cooking vessel with handle (pan (US)), with angled sides.)
• paper towels (US) are kitchen towels or kitchen roll in other countries.
• dish towels (US), aka kitchen towels (US) or tea towels (UK, AU, NZ), are reusable cloth towels.
• Kitchen bench (AU) is the kitchen counter (US), worktop (UK).

Units of measurement & sizing :

• teaspoon (US,UK, CA) is 5 mL (note: abbreviated 't' or 'tsp')
• dessert spoon (UK) is 10 mL (although may have historically been closer to 15mL)
• tablespoon (US,CA) is roughly 15 mL (note: abbreviated 'T', 'TB', or 'tbsp') but a tablespoon (UK) is 17.7mL and tablespoon (AU) is 20 mL. Historical British cookbooks may use an ~25mL tablespoon. (more details).
• A stick of butter (US) is 1/4 lb (113 g); the physical stick is marked into eight "tablespoon" divisions [slightly larger than an actual tablespoon, roughly 14g each]
• A knob of butter (UK) is somewhere around 2 TB (US), but is an inexact measure.
• A pat of butter (US) is between 1 and 2 tsp (5 to 10 mL), most commonly 48 per lb, or ~1.5 tsp. (~9.5 grams, 7.5mL)
• A cup (US) for cooking is a fixed measure of ~236mL (8 fluid ounces, 16 TB, 1/2 a US pint); A British Imperial cup is 1/2 of an Imperial pint (~284mL) Other countries may use a 225mL 'cup' or 250mL 'metric cup' (AU, and some regions of CA?)
• A cup of coffee or tea (when measuring electric kettles) may be based on 5 or 6 oz 'cups'. Always look for the volume in mL or L when buying such items.
• A cup of uncooked rice (for rice cooker instructions) is 175mL, roughly 3/4 of a US cup.
• A pint (UK, AU) is 20 Imperial fluid ounces (568.261 mL), while a pint (US) is 16 fluid ounces (473.176 mL).
• A gas mark (UK) refers to the dials on some British gas ovens (Farmhouse Cookery). The marks from 1 to 9 correspond roughly to 275 – 475 °F (at 25 °F intervals) or 140 – 250 °C (at 10 °C intervals) (more detail below)
• A tin (UK) of tomatoes is the sized tin can (in US, just called a "can") that it's typically sold in. For many vegetables, this is a 400mL / ~14oz container, but is not a constant (for example, anchovies or tomato paste). (ref; see below)
• Unless otherwise qualified, assume an egg is about 60 grams. (a 'large egg' (US,CA), but a 'medium egg' in Europe). (ref)