(countable) Anything that seems to be something that it is not. / (countable) A misapprehension; a belief in something that is in fact not true. / (countable) A magician’s trick.

Under an illusion; deceived.

In a illusive fashion.

The quality of being illusive; deceptiveness; false show.

Subject to or pertaining to an illusion, often used in the sense of an unrealistic expectation or an unreachable goal or outcome.

plural of illusion

An optical illusion in which an arrangement of horizontal and vertical bars of various lengths may be viewed as either a series of rectangles or a series of circles.

A cognitive bias by which people wrongly think that they have direct insight into the origins of their mental states, while treating other people's introspections as unreliable.

An optical illusion involving the misperception of the position of one segment of a transverse line that has been interrupted by the contour of an intervening structure.

(linguistics) A kind of comparative sentence that superficially seems acceptable but actually has no clear meaning. Example: "More people have been to Russia than I have."