al‧ter e‧go /ˌæltər ˈiːɡəʊ, ˌɔːl- $ ˌæltər ˈiːɡoʊ, ˌɒːl-/ noun [countable]
[Date: 1500-1600; Language: Latin; Origin: 'other I']

1. sb’s alter ego an invented person that you use to represent part of your character that is very different from your usual one:
Gissing used his fictional alter ego to attack Victorian morals.

2. someone you trust and who has similar opinions, attitudes etc:
Mrs Reagan was widely regarded as the President’s alter ego.

[TahlilGaran] Dictionary of Contemporary English ▲