A random insult word. It's used especially by those who are deeply involved in their trig homework, though it really has no definite meaning.
*Phil is silently doing his trig homework*
*Jackie spills his snack all over the lunchroom floor*
*Phil jumps up*
Phil: YOU ASSTANGENT!
Jackie: What the hell is an asstangent?
Phil: I have no idea.
(true story =P)