Knuckle Slipping Share definition Flag To have your nipples sucked while hanging from the monkeybars. After class one night two frisky law students walked to the park and he started knuckle slipping her. Knuckle Slipping by CrackerJax78 April 1, 2010 0 0 Get merch Get the Knuckle Slipping mug. Buy Now — $32.95 See more merch