alter ego

1. Another name or identity that one assumes. He's a clean-cut accountant during the week, but on the weekend he indulges in hedonistic pursuits as his alter ego "Jack." Journalist Clark Kent is, of course, better known by his famous alter-ego, Superman. I had no idea John had this punk rock alter-ego, Johnny Bones! Is he really in a band?

2. A separate or different aspect or element of one's personality, identity, or psyche. For such a quiet woman, she has a rage and temper at times that is like some alter ego. I'm very shy in person, but, in my writing, a vivacious alter ego comes out to play. I'd never seen him lash out like that before—it's like he had an alter ego or something.

3. A close, inseparable friend of very similar attitudes and interests. My girlfriend and I are so similar, we are like each other's alter ego. I didn't think I would survive Liz's death. We'd met in second grade, so we'd been basically alter egos our whole lives. I have plenty of friends, but no one really gets me like Sophie does. She's like my alter ego.

4. A person who acts as a substitute for or copy of another person; a doppelgänger. Owing to failing health, the dictator has left his son to run the country for the past month, essentially operating as his alter ego. I'll be filling in for your teacher for the rest of the week. Just think of me as her alter ego! No one respects him because he thinks he's some bigshot when he's really just the boss's alter ego in her absence.