Used for someone deeply passionate about a specific hobby, activity, or subculture. Often appears in compounds like 映画フリーク (movie buff) or ダンスフリーク (dance freak).
He's a fitness freak and goes to the gym every day.
あの映画フリークは年間300本も観るらしい。
That movie buff apparently watches 300 films a year.
freak; monster; deformed creature
Refers to a physically abnormal or monstrous being, often in a fictional or sensational context. Can be derogatory when applied to people; use with caution.
そのホラー映画には、サーカスのフリークが登場する。
In that horror movie, a circus freak appears.
freakshake
Loanword from English 'freak', borrowed into Japanese with the same range of meanings: enthusiast and abnormal creature.