illusory
adj.seeming to be real or true, but actually being false or not lasting. You use this to describe things that trick your mind or senses.
adj.giving a false impression of reality or truth; deceptive. Often describes hopes, beliefs, or perceptions that are not grounded in fact.
“The success of the new product was only an illusory victory.”
“The calm before the storm gave an illusory sense of safety to the people living on the coast.”
“Economists warned that the sudden rise in stock prices was an illusory bubble that would eventually burst, leaving investors with significant losses.”
Borrowed from Middle French illusorie (modern French illusoire), derived from Latin illūsōrius (“mocking, ironical”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.