An absolutely insane fight broke out at a card room in California this week ... and it all appeared to start because a man dropped a "Yo Mama!" insult on another man.
The wild scene reportedly went down at HUSTLER Casino in L.A. ... after two guys got into a verbal argument at a poker table inside the venue for unknown reasons.
Video from the casino shows the two screamed at each other ... and escalated into a full-on fistfight when one of the men fired off a jab about the other man's mother.