\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.