biffin Share definition Flag The small area between your balls n your bum. Between ur balls n your bum theres a biffin, its a place where you shouldn't be sniffing. biffin by Master One August 27, 2003 Words you can keep railfan mug chonk mug chud mug based mug 67 mug slime mug mogging mug chopped mug thot mug glazing mug huzz mug yams mug larp mug unc mug cracked mug simp mug baddie mug bop mug lolcow mug