not genuine

counterfeit

(to make) (something) made or done in imitation of another thing in order to deceive

fake, simulated

(of a performance, performer, new design etc) wonderful; excellent

amazing, wonderful

a work of art etc that looks genuine but is not

false, imitation

(of an argument etc) wrong because based on error

false, wrong

(of a person) led by imagination instead of reason and experience

imaginary, romantic

based on a false or impossible idea

deceptive

to pretend (to be in the condition mentioned)

artificial, counterfeit

imaginary; not real

fake, make-believe; hypothetical

false; disloyal

dishonest