Knuckin the 'B' Share definition Flag Going atleast one knuckle deep into a butthole. Preferably done to the opposite sex during intercourse. Dude, while I was railin that chick out last night.. I started knuckin the 'B' and she loved it!! Knuckin the 'B' by HBK and JIMMY May 8, 2010 0 0 Get merch Get the Knuckin the 'B' mug. Buy Now — $32.95 See more merch
