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2.
when a male or female is fingering his or her woman:
he/she places 4 fingers inside the girl with a flat hand resembling a sharks fin. then making wave like motions with the hand when all of the hand other than the thumb is inserted.
shark finned fuck out that bitch last night!
i was hefty shark finning at the weekend
by RamboJambo123 August 11, 2009
 
1.
When you float on your back in a body of water with an erection that sticks out like a shark finn.
I'm gonna go shark finning around that bitch in the deep end of the pool.
by D-Rye August 05, 2013
 
3.
Verb
To swim backstroke with an erection.
'Did you see Ralph? He was totally Shark Finning it over that lifeguard.'Said Paul.
by SickyMike October 17, 2014