one who associates so closely with a given person as to assume that person's mode of behavior, personality, beliefs, etc.
Words nearby second self
Origin of second self
First recorded in 1580–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020
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