WordNet (r) 3.0 (2006):

twat
    n 1: a man who is a stupid incompetent fool [syn: fathead,
         goof, goofball, bozo, jackass, goose, cuckoo,
         twat, zany]
    2: obscene terms for female genitals [syn: cunt, puss,
       pussy, slit, snatch, twat]