The definition of illusory is made to be or related to something fake or deceptive.
An example of something illusory is a wild tale of science fiction; an illusory tale.
producing, based on, or having the nature of, illusion; deceptive; unreal
Produced by, based on, or having the nature of an illusion; deceptive: an illusory belief that their finances would improve.
(comparative more illusory, superlative most illusory)
From Middle French illusorie
illusory - Legal Definition
Deceptive or insubstantial.illusory promise
A promise to do something that is unenforceable or meaningless because the promisor has means of avoiding the commitment.