a sexually desirable girl in early adolescence
Between … nine and fourteen there occur maidens who … reveal their true nature which is not human but nymphic … and these chosen creatures I propose to designate as ‘nymphets’ — Vladimir Nabokov
French nymphette, dimin. of nymphe: see nymph. Orig a poetic word for a young nymph; the current sense was introduced by V Nabokov d.1977, Russian-born American writer, in his novel Lolita