1. Excessive or neurotic admiration of oneself; self-love or self- admiration.
2. An abnormal interest in oneself; especially, in one's own body and sexual characteristics; self-love or self-admiration.
3. Sexual pleasure derived from observing one's own naked body.
4. In psychoanalysis, sexual self interest that is a normal characteristic of the phallic stage of psychosexual development, occurring as the infantile ego acquires a libido.

Narcissism in the adult is abnormal, representing fixation at this phallic stage of development or regression to it.

5. Etymology: from German Narzissismus, coined in 1899 by German psychiatrist Paul Näcke (1851-1913) in Die sexuellen Perversitäten, on a comparison first suggested in 1898 by Havelock Ellis, from Greek Narkissos, the name of a beautiful young man in mythology (Ovid, "Metamorphoses," iii.370) who fell in love with his own reflection in a spring and subsequently was turned into the flower now known as a narcissus.

There is an apparent disagreement as to who "coined" the term narcissism because according to Dr. Ernest Klein, the term narcissism, as used in psychology, came from German Narzissismus; coined by Sigmund Freud (1856-1939), founder of psychoanalysis.