TB or "That/The Bastard": derived from English words:
That: used to indicate a person, thing, idea, state, event, time, remark, etc., as pointed out or present, mentioned before, supposed to be understood, or by way of emphasis
Bastard: a vicious, despicable, or thoroughly disliked person
is usually used to describe a person of questionable parentage, or unpleasant disposition.
text message between author and girlfriend, circa January 2008.