noun
Refers to a person or thing that is not genuine; often used for people pretending to be someone else, but also for counterfeit goods.
あの人は偽者だ。
That person is an impostor.
このブランド品は偽者かもしれない。
This branded item might be a fake.
Compound of 偽 (nise, 'fake') + 者 (mono, 'person'). The kanji 偽 means 'falsehood' or 'imitation', and 者 is a common suffix for people.