Sentence:  Doom has three running speeds (not counting <WSD>wall humping</WSD>): running, strafe-running, and strafe-drawing. Strafe-drawing is a little faster than strafe-running, but harder to control for distance. 
Meaning of the word marked with <WSD> tags:  (The act of a character) moving repeatedly against a wall, as if humping it, either intentionally (e.g. trying to find secret doors) or due to a glitch.