This is next-level pervert peeping tom/mooning (showing one's ass).
Rather than a simple peek-a-boo to a victim just trying to get a look the perpetrator wants to be seen and caught in the act. Similar to "mooning" or placing one's bare ass up to a window for comedic value this act encompasses both peeping as well as mooning but much more.
You expose yourself with pants down to the knees or pantless. Press your genitals firmly against the window where the observer on the other side will have a clear and unobstructed view of the upcoming action. Once the attention of the victim has been confirmed the individual preforming the W.W.W.W. will begin to urinate while moving genitals from side to side. If done correctly a squeegee-like sound should be produced from the lateral motion. If ones "package" is of sufficient size it should act like a windshield wiper on a cars windshield (swiping from side to side whilst your penis displaces the urine away from the outside of the window) ensuring the observer maintains clear line of sight with the depravity happening on the other side of the glass.
Dude 1:

"I got wasted last night and wanted to give her and her new boyfriend something to remember me by, I was just going to smear poop on her window but I couldn't help myself when I noticed it was already dirty.... Plus I wanted to show off my shit. I gave em' the ol "
Wet Window Wiener Wiper". Tell me I'm not the fuckin man".

Dude 2:
"Aaron (dude 1) you're the fuckin man, always have been! Legendary bro, fucking legendary."
by Aaron Deez-nutz March 25, 2023
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