team-fortress-2terminologytf2-pyro
There's a more or less subtle reference I'm missing in comics 79, 87 and 131 (pictured below) of Nerf Now!.
What is it about?
[…] There are moments w + 1 is very effective and I dare to say, fun. However, there is a time and a place for everything, and going head-first on half-enemy team isn't one of these times. […]
There are several server options that affect weapon damage in Team Fortress 2, and they're often confused:
Weapon Spread -- With this turned on, hitscan weapons, such as shotguns, will have the same non-random pattern of "bullets" each time they are used. Default is ON.
Damage Spread -- Each weapon normally has a minimum and maximum damage. No Damage Spread means that each weapon will do a set, average, damage rather than varying between attacks. Default is ON. (Critical hits always do 3 times damage)
Damage Falloff -- Normally, the damage dealt by a weapon decreases the farther away you are for your target. If this is turned off, A rocket detonating right next to you and a rocket shot from the opposite side of the map will do equivalent damage. Crits are never affected by Damage Falloff. Default is ON.
The default is to have Damage Spread ON. Nodmgspread refers to servers which have turned it OFF.
You can reflect:
Soldier Rockets (all types)
Pyro Flares (all types)
Demoman Grenades (all types)
Demoman Sticky Bombs (Sticky Bomb Launcher/Scottish Resistance)†
Huntsman arrows (which can headshot enemies) 
Sandman Baseballs Wrap Assassin OrnamentsWhen you reflect projectiles they are promoted to minicrits (if they weren't), change sides with your team and ownership to you (with the exception (†) of stickies). This means, however, that they will still do splash damage to you should they explode too close. As for stickies You can still push those off points and doors, however, or even push them below the demoman's feet.
You cannot reflect:
Best Answer
I've not heard of W+1 specifically, but the more common W+M1 refers to holding W and the primary mouse button (typically with the primary weapon) to run forward spewing fire. They seem to mean the same thing according to the photo notes on #79 and #87, on the W+1 speech bubbles.
It's a common offensive strategy effective with ÜberCharges, but also one that's stereotypically associated with new/bad players (or players new to the Pyro).
You may hear W+M1 in other FPS games too.