Sell out is a popular term used to describe someone who betrays their values or principles for personal gain. People often use sell out when they feel someone has compromised their beliefs for money or popularity. However, there are many synonyms for the term that convey the same meaning. These include phrases like "cave in," "give in," "sell their soul," "back down," "succumb," and "compromise." All these phrases describe the act of betraying one's beliefs or values for some benefit, which ultimately means, selling out. Whether it's in politics, music, or any other field, people frequently use these synonyms to criticize those who sell out their morals.