im ‧ pos ‧ tor BrE AmE ( also imposter American English ) /ɪmˈpɒstə $ ɪmˈpɑːstər/ noun [countable]
[ Date: 1500-1600 ; Language: Latin ; Origin: impostus , past participle of imponere ; ⇨ ↑ impose ]
someone who pretends to be someone else in order to trick people:
The nurse was soon discovered to be an impostor.