beff Share definition Flag To stimulate the clitoris with the tongue (from the genuine Dutch word 'beffen'). I beffed her so good, she squealed like a fire engine. beff by Befborstel King January 18, 2004 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