noun
one who passes himself off as something or someone he is not
the presumed heir was discovered to be an impostor
Synonyms: fake, faker, fraud, humbug, phony, pretender; compare charlatan
Related Word: imitator, mimic; beguiler, deceiver, misleader; cheat, pettifogger, shyster, trickster; hypocrite; charlatan, mountebank, quack; bluffer, dissembler, four-flusher, shammer
Idioms: wolf in sheep's clothing