one who associates so closely with a given person as to assume that person's mode of behavior, personality, beliefs, etc.
What Is A “Self-Own”?There aren’t many better places, it seems, to celebrate the mistakes of others than on social media. Naturally, this is the arena where self-own has had great popularity. So, what does it mean?
Origin of second self
First recorded in 1580–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for second self
Was it his counterpart, or second-self, that made him feel that evening as though he had never known himself?Dawn|Mrs. Harriet A. Adams