Starcraft is a real-time strategy game, and Zerg is one of three factions you can play in the game. Zerg units are individually weak but cheap compared to the other factions, so Zerg players typically compose swarms of disposable units when staging and conducting attacks. It’s also quicker to make large swarms, since there isn’t a sequential build queue for Zerg unit construction. It makes for a pretty interesting switch in mindset compared to the other sides, where there is much more emphasis on preserving one’s units. Some of the more obnoxious strategies, like the Zerg rush, have become memes among gamers.

>Zerg units are individually weak but cheap compared to the other factions

And fast. So. fucking. fast.

I hate playing against Zerg.

This is also apt:

The term "Zerg Rush", or "zerging", is now commonly used to describe sacrificing economic development in favor of using many cheap, yet weak units to overwhelm an enemy by attrition or sheer numbers.

— Wikipedia

It's a StarCraft reference.

https://starcraft.fandom.com/wiki/Zerg

"The Zerg Swarm is a terrifying and ruthless amalgamation of biologically advanced, arthropodal aliens. [...] They are named "the Swarm" per their ability to rapidly create strains, and the relentless assaults they employ to overwhelm their foes."

Zerg is a playable race in the game Starcraft. They are bio units where everything you build is biological.

This is one of the three main factions in StarCraft. Think hiveminds and bugs.