* Nonconformist: This is a general term and probably the closest single word. It simply means someone who doesn't conform.
* Maverick: This implies a nonconformist who is independent and possibly rebellious.
* Rebel: This suggests a more active and defiant rejection of norms.
* Dissident: This term usually applies to someone who opposes official policy, often politically.
* Iconoclast: This describes someone who attacks cherished beliefs or institutions.
* Deviant: This term carries a more negative connotation and suggests behavior that is outside social norms, potentially harmful or criminal.
The best word to use will depend on the specific situation and the reason for the person's nonconformity.