Illusion \Il*lu"sion\, n. [F. illusion, L. illusio, fr. illudere, illusum, to illude. See Illude.]

1. An unreal image presented to the bodily or mental vision; a deceptive appearance; a false show; mockery; hallucination.

To cheat the eye with blear illusions. --Milton.

2. Hence: Anything agreeably fascinating and charning; enchantment; witchery; glamour.

Ye soft illusions, dear deceits, arise! --Pope.

3. (Physiol.) A sensation originated by some external object, but so modified as in any way to lead to an erroneous perception; as when the rolling of a wagon is mistaken for thunder.

Note: Some modern writers distinguish between an illusion and hallucination, regarding the former as originating with some external object, and the latter as having no objective occasion whatever.

4. A plain, delicate lace, usually of silk, used for veils, scarfs, dresses, etc.

Syn: Delusion; mockery; deception; chimera; fallacy. See Delusion. Illusion, Delusion. Illusion refers particularly to errors of the sense; delusion to false hopes or deceptions of the mind. An optical deception is an illusion; a false opinion is a delusion. --E. Edwards.

Source: Webster's Revised Unabridged Dictionary (1913)