Narcissistic personality disorder refers to Cluster B (dramatic, emotional, or erratic) personality disorder involving a pervasive pattern of grandiosity in fantasy or behavior, need for admiration, and lack of empathy.
Other /More definition:
Narcissistic personality disorder refers to a personality disorder primarily characterized by an unrealistic, inflated sense of self-importance and a lack of sensitivity to the needs of other people.
Lexicon of Psychology - Terms, Treatments, Biographies,