sellout

(noun) a person who betrays his or her beliefs

Example Sentences:

At the nightclub, Sarah’s friend left her alone to dance with a sexy guy. Her friend is a sellout.

Ben has been a vegetarian for his whole life. When he started eating meat, his friends called him a sellout.

From the Blogs:

Wright’s Bargain is a Sellout

Media:

Similar idioms:

1. birds of a feather, flock together
2. drive a hard bargain
3. dead set against something
4. call one’s dogs off