Tank

 generally refers to one of the following:

Locations:

 * Burger Tank ― A fast food restaurant chain in the Left 4 Dead universe. The Survivors can sometimes find supplies as well as Rescue Closets located in these restaurants.

Special Infected:

 * The Tank ― One of the main bosses featured in both games of Left 4 Dead, it is a Special Infected of gigantic proportions, and the most powerful Infected.

Gameplay:

 * Propane Tank ― Canisters that can be found throughout both Left 4 Dead games and will blow up with an explosion similar to that of a Pipe Bomb when shot.
 * Oxygen Tank ― Similar to the propane tank; however, instead of exploding instantly like the propane tank, they will vent gas for a period of time before exploding.
 * Dead City/Military Outpost ― The fourth level of the custom campaign Dead City, whose Crescendo Event involves refueling a tank.

Achievements:

 * SEPTIC TANK ― Is an achievement earned in Left 4 Dead 2 when a player throws a Bile Jar on a Tank.
 * TANKBUSTERS ― Is an achievement earned in Left 4 Dead when the Survivors defeat a Tank without anyone taking any damage from the Tank.
 * TANK STUMBLE ― Is an achievement earned in the Left 4 Dead DLC Crash Course where the Survivors shoot a propane tank at a nearby Tank causing it to be stunned.
 * MAN VS TANK ― Is an achievement earned in Left 4 Dead when a single player defeats a Tank singlehandedly, without assistance from the other Survivors.
 * TANK BURGER ― Is an achievement earned in Left 4 Dead 2 when the Survivors defeat the Tank using only melee weapons.