The crossword solution for the term 'HE'S NOT HIMSELF' is ACTOR, which is a five letter word. An ACTOR is someone who performs in a play, movie, television show, or other form of entertainment. They often take on the role of a character and act out the story or script. The phrase 'HE's not himself' is often used to describe someone who is acting differently than usual, suggesting that they are not in their normal state of mind.