1.VerbTo untruthfully speak of another in a belittling, deprecative, slighting manner, either in person or in absentia.
"Talk shit, get hit."
2.VerbTo speak nonsense or to lie.
"Yo, man, Bobby was here, an' he was talkin' all kinds of shit about how many girlfriends he's had; y'all know that he ain't had a girlfriend since a girl had him."