Widely used in the Bay Area, means to whoop/beat down someone badly in a fight. It can even be used when you beat your friends in a game.
Also known as tearing shit up, In gaming it could be known as a synonym for getting owned(Pwned).
Person #1 "Yo cuz, your a poodle, Ill punk you and your homies, come see me bout somethin!"
Person #2 (talking to person #3) "Is this guy yappin his mouth, yo G, lets Molly Whop this sucka"
"Man you play too much, and if you play to much by talking the talk and by not walking the walk then you finna get Molly Whoped!"
"Did you see David, he came through Molly Whoppin up." - (This version was used in a different way, he came through looking better and harder than anyone else and beating them in style. aka stunting)
"Whats up patna, you wanna rumble with us, then your ass is getting molly whopped!"