1. wanker
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While "to wank" means "to masturbate", the term "wanker" is seldom if ever used in British slang to denote "one who wanks". It is quite wrong to infer from somebody's being a wanker that they in fact wank (and vice versa), but of course, fair to assume they do in any case. Herein lies the genius of the insult: if you call someone a wanker, it's probably true, but only literally.