knuckle spider

A knuckle spider is the act of rapidly using your fingers in a spider-like motion while simultaneously inserting your fingers inside a woman's vagina with the intent of granting her intense pleasure.

Friend: "Yo, what did you get on the test?"
Guy: "A+"
Friend: "WTF? How? I thought you said you bombed it?"
Guy: "Yeah, I really needed that A so I went in after class and gave our teacher the ol' knuckle spider" (makes spider-like hand gesture)