A tactic used in Blizzard's 1998 release of "StarCraft." The Zerg were one of 3 playable races, bug-like creatures that created units through evolution, morhping, and hatching. The Zergling was the basic infantry unit, capable of only melee attacks. However, in a multiplayer situation, a single larva (the basic unit from which all Zerg units morph) will morph into two Zerglings, creating a cheaply made swarm at a rapid pace. Used for quick ends to multiplayer games and is often referred to in both negative and postive lights.
He wiped out my SCV's and my command center in 90 seconds flat with a Zergling Rush.
n,v. To overwhelm an opponent through the use of cheaply made units at the expense of any long-term strategy (taken from Blizzard's "StarCraft").
"I'm an expert at being the Zerg; the first thing I do is hit 'em with a Zergling Rush."
"Just Zergling Rush them. It totally catches them off guard."