A variation on the "middle finger" obscene gesture. The wrist is cocked at a 90 degree angle and only the middle finger is extended straight in the air. Generally considered to be a more elegant way to express "<screw> you".
Steve and Mike gave Andy the Wallace Presentation when Andy asked them to pick up the tab.
Someone who boasts about their accomplishments when in fact they have nothing to boast about or when a man is hitting on a woman and lies about how big his penis is or how good he is in bed.