Lysergic acid diethylamide, LSD, LSD-25, or acid, is a semisynthetic psychedelic drug of the ergoline family. Its unusual psychological effects, which include illusions of colored patterns behind the eyes, a sense of time distorting, crawling geometric patterns, and the loss of the user's sense of identity has made it one of the most widely known psychedelic drugs. It has been used mainly as a recreational drug, an entheogen, and a tool to supplement various practices for transcendence, including in meditation and illicit, formerly legal psychedelic therapy.