scum

Universal Words noun 1 [U,sing.] a layer of bubbles or an unpleasant substance that forms on the surface of a liquid: Skim off any scum. * stinking water covered by a thick green scum 2 (informal) [pl.] an insulting word for people that you strongly disapprove of: Don't waste your sympathy on scum like that. * Drug dealers are the scum of the earth (= the worst people there are). scummy adjective: scummy water * scummy people dropping litter