il•lu•sionɪˈlu ʒən(n.)

1. something that deceives by producing a false or misleading impression of reality.

2. the state or condition of being deceived; misapprehension.

3. an instance of being deceived.

4. a perception, as of visual stimuli

   Category: Psychology

   Ref: ( optical illusion )

5. a delicate tulle of silk or nylon having a cobwebbed appearance, for trimmings, veilings, and the like.

6. Obs. the act of deceiving.

Origin of illusion:

1300–50; ME < L illūsiō irony, mocking, der. of illūdere to mock, ridicule =-il-il1+lūdere to play

il•lu′sion•al(adj.)

il•lu′sion•ar`y(adj.)