Learn English – The differences between: deliver, ship, and transmit

Defining the word "sarcasm" is fairly straightforward. It usually means the expression of a sentiment whose opposite is meant. For example:

Hooray! I have a headcold.

Irony, however, eludes a simple explanation, and there tend to be disagreements about its meaning between UK and US speakers. Irony is found in the contrast between expected, or ordinary, outcomes and what actually happens. The greater the distance, the greater the irony.

For example: In this video, the police officer is giving a lecture on firearms safety, and shoots himself in the leg: http://www.youtube.com/watch?v=am-Qdx6vky0

That's an example of situational irony. And note that irony need not be funny, although it often is.

I looked up each and everyone of their meanings, and they all had meanings of "crude, unrefined", and when I looked up "unrefined" it had the meaning of "crude".

So I looked up "crude", and came up with:

Lacking tact or taste/Lacking concealing elements.

Basically, they all mean the same thing, and that is, just not being tactful, and putting things in an unpleasant way.

In their relation to the third and second senses above, they are all as I said, an antonym of refined, but it does not necessarily mean these words denote "obscenity". They may be offensive, yes, or unpleasant, but "obscenity" includes much worse things like blasphemy, or cursing, or highly derogatory terms, whereas your list of words lean more to being dysphemistic.