freak

To freak is to act out or to cause someone to act in a wild manner or to become very upset, agitated or excited. (verb)

An example of freak is someone who is dancing around and shouting and screaming because he has just won the lottery.
An example of freak is when someone gets very angry and starts yelling and breaking things for little or no reason.
An example of freak is when you say something to someone that causes him to become upset and start yelling and acting overly excited.

A freak is an unexpected event or a person who does not fit in with the mainstream. (noun)

An example of freak is a snowstorm in July.
An example of freak is an outcast who doesn't fit in with anyone and who everyone stays away from because they find them to be odd.

See freak in Webster's New World College Dictionary