A beat biter is a person who copy your phrases or anything like that. Okay a beat biter is some one who takes the shit that you have created or that you have begun to use, whether it be phrases or favorite food or whatever.
Nick: Oh WOW
Amanda: Oh WOW you are a damn beat biter shit taking my shit I have been using wow since forever.
Nick: I ain't beat biting woman that's just my new phrase
Amanda: Yeah your new phrase that you got from ME!