to place ones finger, in ones bum whilst under instruction to only place fingers in the vagina.
"OH MY GAWD, MEXICAN! WHY DID YOU FINGER -BUM ME!! THERE WAS NO BUM CONSENT!"

Good ol'Finger-Bum
by Dan&Indi February 19, 2016
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The 11th finger that comes out of a girl's bum to enter a guy's bum while they are having sex.
The sex was pretty bland until her bum finger crept out.
by Sebastian Rofo December 7, 2013
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