A group of personality disorders in the DSM-5 characterized by dramatic, overly emotional or unpredictable thinking or behavior: narcissistic personality disorderNarcissistic personality disorder A mental condition in which people have an inflated sense of their own importance, a deep need for excessive attention and admiration, troubled relationships, and a lack of empathy for others. Also see Narcissistic abuse., antisocial personality disorder, borderline personality disorder, and histrionic personality disorder.