Named after a dude with terrible personal hygiene and more STD's than a crack whore in Amsterdam, that is attempting to get lucky at the bar. "A guy who is engaging the town whore in sexual intercourse in the out house "biffy" outside the local bar. After he finishes he leaves the whore in the biffy and tips it over on the door so the whore cannot escape."
Dude 1 "Hey man I gotta take a piss"
Dude 2 "Lets hit the biffy outside the line is too long in here"
Dude 3 "We should but shitter is out of commission, some guy dirty dulon'ed a hoe last night"
Dude 2 "That must've been one slutty hoe"
A Dirty Dylan is when play-fighting with your girlfriend, you finish it by pinning her down and farting on her head, staying sat on her face for a while so she has to smell.