To insert one's finger into another's well lubricated anal or vaginal orifice, imitating the rocking motion of conventional sex. See also fingerbang.
"Billy fingerfucked Amy's bung so hard that crap shot out!"
To slowly, but surely, slide/ram/insert/thrust your finger/fingers into the vagina or into the ass(anus) and will undoubtedly cause extreme pleasure to whoever is recieving the fingerfucking.
"Fingerfuck your pussy like you want some, girl
Work it like a nigga straight licking on your pearl
I wanna see you cum in the middle of the dance floor
A nigga can't fuck, what you think your finger made for???
I'ma beat that pussy up
You get it wet enough, I might lick it up
Lickey, lickey, lickey, like a peppermint swirl
Lick that clit