talk shit

verb2

1. •
   (slang, vulgar) To untruthfully speak of another in a belittling, deprecative, slighting manner, either in person or in absentia.

   • Talk shit, get hit.
2. •
   (slang, vulgar) To 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.