In military strategy video games and board games, a doomstack (also a verb, "to doomstack") is a remarkably large quantity of military units, often all of the same type and/or all low-ranking units, that are all placed in a "stack" on the same tile or space of the game board and moved together as a single unit.
In its most basic form, doomstacking is a way to avoid defeat in detail by numerically inferior but perhaps qualitatively superior (quicker or stronger) forces. It is also a method used by players with less strategic acumen to attempt to simplify the game and overpower smarter players with sheer numbers. Lastly, it can be a way for a player with an advantage in unit production, but perhaps a disadvantage in technology, to attempt to leverage their superior production to achieve victory.