The act of taking one's tongue and inserting it into another's said ear.
Charles: Oh shit, my ear still feels wet.
Jose: Told you not to mess with me, homez.
Charles: Fuckin' wet willy sr.
Jose: It's the goddamn muthafucking Wet William Sr., bitch! Bliggity bl-ow!
someone putting their wet, ugly, disgusting, crusty, no-good, dirty, slimy, slim jim ass, finger in your waxy no-good ear and twisting it till it hurts.
john: "wet willies"
will: why tf did you give me a wetwillie john: bec-
will: oh is see, my because my name is will