peanut butter knuckle fuck Share definition Flag When another person, or animal, licks peanut butter off your balls while you jerk off. Man, my girl gave me a peanut butter knuckle fuck last night. peanut butter knuckle fuck by Britt Charnock March 6, 2017 0 0 Get merch Get the peanut butter knuckle fuck mug. Buy Now — $32.95 See more merch