multiple personality
From Longman Dictionary of Contemporary Englishmultiple personalityˌmultiple personˈality noun [countable] if someone has a multiple personality, they are mentally ill because they have two or more completely separate personalities that each behave differently → split personality multiple personality disorderExamples from the Corpusmultiple personality• He pulls the old multiple personality excuse.• On one end is daydreaming, on the other, multiple personality.