1 [count] : the person that someone normally or truly is —used to describe the way someone acts or feels ▪ He's just not his usual/normal self today. ▪ She was her old self again after some sleep. [=she returned to behaving/feeling as she normally did after some sleep] ▪ He was a mere ghost/shadow of his former self after the illness. [=he was much weaker after his illness] ▪ She showed her true/real self. [=she stopped pretending and showed what type of person she really was]
2 [count] : a particular part of your personality or character that is shown in a particular situation ▪ She showed her better self at the party. ▪ Her public self is very different from her private self. ▪ He started taking yoga and meditation classes to get in touch with his inner self. [=the emotional and spiritual part of himself]
3 [noncount] : the personality or character that makes a person different from other people : the combination of emotions, thoughts, feelings, etc., that make a person different from others ▪ We each develop a unique sense of self. [=a unique idea about who we are] ▪ Philosophers have written about the conception/idea of the self.
4 [noncount] formal : your own personal interest or advantage ▪ She helped without any thought of self. [=without any thought of trying to make things better for herself]
5 [count] —used to refer to a person ▪ a photo of her younger self ▪ He puts his whole self into each and every game. [=he tries very hard to play his best in each game] ▪ (informal) “Go get me another beer.” “You can get it your (own) damn self!” ▪ (informal) I could barely drag my sorry self out of bed.