Freak is a not-so-nice noun that refers to either a person who expresses such an intense obsession with something that it resembles addiction, or a person or animal that is monstrous and deformed.
Synonyms for freak, when used to describe something or something abnormal, include anomaly, chimera, misshape, and oddity. Weirdo is slang for freak, and regular is its antonym. People who ardently adore a particular type of music, like heavy metal, or who have many piercings or identify with a subculture, are often labeled freak. A freak occurrence, on the other hand, is not necessarily a bad thing, but connotes something irregular or unexpected. A freak of nature can lead to thunder-snow, and a freak accident can lead to, well, a missing ear or toe.