When two individuals engage in oral sex immediately after having sexual intercourse. Derived from the animal itself, ducks eat the stuff off the grass after a rainfall, like oral sex after sex.
"you wanna duck fuck?"
The aftermath of a brutal pounding in which the female waddles around like a duck for weeks or even months at a time.
Jenny: Hey, Liz why are you walking like that?
Liz: Frank duck fucked me so hard last night.