sham; fraud; counterfeit; impostor; pretender
Refers to a person or thing that is not genuine; a fake, phony, or impostor. Often used in a derogatory sense.
He claims to be a doctor, but he's actually a fraud.
I immediately knew that antique was a counterfeit.
詐欺師 specifically means 'swindler' or 'con artist', focusing on the act of defrauding others for financial gain. 似非者 is broader, covering any kind of sham or pretender.
似非 (ese) means 'pseudo-' or 'sham', and 者 (mono) means 'person'. The exact origin of 似非 is uncertain, but it has been used since classical Japanese to indicate something false or pretended.