To perform an exaggerated gesture of male masturbation with one's hand in the air in front of oneself. Meant usually as a insult to somebody to whom it is directed, or as a symbol of annoyance at something which has been said. See also am.
Jim: Dude, u sux hardcore at CS!
Bob: Hey Jim, guess what? <performs air masturbation>
its when you pretend the air is a penis and then you just masturbate it. if you need help come and see me.
air masturbation is where you go up down up down up down