A compstomp is a gaming match where all human players ally against the AI computer, hoping to absolutely crush, or ‘stomp’, the opponent AI.
One classic compstomp mode from Starcraft features matches with 7 human players versus 1 AI opponent, sometimes with all 7 human players occupying a fortified starting position – depending on how cruel the humans want to be against the AI for that match. A fun variant of the compstomp mode occurs when one or more of the human players unally from the others, which almost always devolves into a ‘last-man standing’ scenario.
Compstomp matches used to be abused by players trying to artificially boost their MMR, especially in the heyday of Broodwar, but most modern games have stopped providing increases to MMR when playing against AI enemies.