A tasteless attempted insult or mockery that backfires completely. Usually resulting in embarrassment on the part of person the oppisult originated from. The oppisult is an epidemic among middle and high school students that is cured best buy a punch in the face.
Black person (to a friend) : "... yo Homie..."
White tween girl (passing by and speaking to her friend) : "YOOOO Homie Biscuit, word up DAAAAWG!" (throws up unidentifyable gang symbol)
White girls friend : " You just oppisulted yourself... Why aren't you at recess?"