The act of taking one's tongue and inserting it into another's saidear.
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!
In the same family as its cousin the 'wet willy,' the Wet William is the act of punching your junk while your significant other is sound asleep, maneuvering your near-ejaculating penis up to their ear, and busting your load.
Oh that? I was bored and you were asleep, so I had no choce but to deliver you a plentiful load of Wet William.
A wet william is a step up from a wet willy. Instead of licking just the tip of your index finger, you place the entirety of your finger in your mouth. Once the finger is fully moistened with saliva, you place it into someones buttox. The warmth of the rear and the moistness of the finger, in correlation to one another, create the feeling of oneness of the two bodies.
Person 1: "Oh man, those sigma chi's are notorious for giving wet williams."
Person 2: "Yea, my life and anus will never be the same."