Similar to a <wet willy>. The diffrence being the moisture on the finger being inserted into one's ear canal is not saliva but instead male seminal fluid from the vagina post intercourse.
I snuggled with Billy after sex as just as he fell alseep I gave him the filthy willy. BOW!!
by SeriouslyLiz June 13, 2008
a Filthy Willy is performed when two straight guys that can make sexual mating calls in the form of a cackling llama have a lapse in sexual judgement. They confuse each other with loud llama noises until one of them reaches around the other for some fantastic ass-play. The other partner then engages in a reach around as well. They continue until one of them defecates on the others chest. Both partners then smear their excrement and scent on one another and have a sword fight to see who will be the bitch and who will wear the pants in their new found gay relationship. They finish the Filthy Willy by holding each others cocks and sticking their thumbs in their mouths as they moan and orgasm themselves to sleep.
Dan asked Will to come over and hang out and play some poker, little did he know that Dan was planning on setting him up for the Filthy Willy and poking him!
by DJ Joey Baggs July 27, 2010