FUP Share definition Flag Acronym for Fat Upper Pussy, the roll of fat located just above a chunky woman's crotch. See also Vagbag I woulda banged her accept for that nasty FUP. FUP by Crum March 28, 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