Meaning of derealization

de•re•al•i•za•tion

Pronunciation: (dē-rē"u-lu-zā'shun), [key]
— n. Psychiatry.
  1. an alteration in perception leading to the feeling that the reality of the world has been changed or lost.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.