The Hardy Brothers are in a nasty family feud -- with Jeff not only trashing his brother Matt ... but also going after his wife, calling her a "witch bitch" who's tearing the family apart.
It all went down on the "TMZ Sports" TV show -- when the wrestling superstars were talking some serious smack to each other leading up to their "I Quit" match on TNA Impact Wrestling tomorrow on PopTV.
It started off with the usual threats ... but got crazy personal when Jeff brought up Matt's wife .