flub Share definition Flag Acronym FLUB - Fat Lazy Useless Bastard. Someone who is overweight, lazy and totally incompetant. My god Derek is a flub he would fuck up a brand new cunt the fat bastard. flub by Mr Fletcher April 9, 2006 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