1. Causing illusion; deceptive; misleading.
2. Of the nature of an illusion; unreal.
Phantasm and illusion spring up quite frequently in fantastical stories and weird tales. Often they wind up being real, and deadly. “Illusory” may not be that uncommon a word, but it’s one that can be wielded to great effect and in more ways than one. A mirage may be illusory, and so may be a promise or a report.
Not to be confused with “illusionary.” I’m looking at you, Magic the Gathering fans.
Not only Hewitt, but his badly frightened native bearers, had been witness to this startling transformation. And to top the whole thing, to remove it definitely from the realm of illusory phenomena, Hewitt claimed that the man-beast had left, startlingly clear in the soft, wet ground, the prints of the paws of a hyena!
– A. Merritt, “The Drone Man” (1936)