A wad of chewed up chewing tobacco that has been spat out on the ground such that it looks like a dog turd. These are most frequently seen around golf courses and people will declare that someone has not cleaned up after their dog when upon closer examination it is determined that it is in fact a mouth turd.
Golfer 1: Dude watch out, don't step in that dog crap !! I can't stand it when people don't clean up after their dog !
Golfer 2: Relax man ! It's just a mouth turd.