"Acts the part" is a phrase used to convey the impression that someone is performing a role or pretending to be something they are not. Antonyms for this phrase include "authentic," "genuine," and "sincere." When someone is authentic, they are being true to themselves and not pretending to be someone or something they are not. Genuine people do not put on a facade or act out scenes for others to see. They are transparent and honest in their thoughts, feelings, and behaviors. Sincerity implies that someone's words or actions come from a place of genuine belief or emotion, and not from a desire to deceive or manipulate others.