A spasm of the buttuck.... Vigorous twitching in the rear and this phenomona only occurs when the sufferer is disturbed or irritated by peers.
Chelsea: "I think we could all use a good grind and hand crank..."
Rob: "I agree lets do that."
Kasey: "You people make my ass twitch..." O___o
Chelsea: "Hoe shit, shes got the Asum spasm..."