Definition of Split personality

Split personality: Multiple personality disorder, a neurosis in which the personality becomes dissociated into two or more distinct parts each of which becomes dominant and controls behavior from time to time to the exclusion of the other parts. A modern name for this condition is dissociative identity disorder.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=11257
Last Editorial Review: 9/20/2012