Jackflip

verb: To perform a backflip while masturbating

OR

noun: A backflip performed while masturbating.

Harrison: OMG Jamie just double jackflipped!!

Astonished Onlooker: WOW! That's two jackflips in a row! Jamie's hella cool!

Jackflip by hbhbhbhbhbhb November 9, 2011

jackflap 

you know that thing that sticks out between a man's legs? that

Jeff's jackflap is huge

jackflap by Johnny Clarkey July 30, 2007