brutus
n. countable C2 Proficiency US //ˈbɹutəs// bru·tus
n. a person who betrays a friend or someone who trusts them. It comes from the name of the man who helped kill Julius Caesar.
n. a traitor or betrayer, specifically one who turns against a close friend or benefactor. Derived from the historical figure Marcus Junius Brutus; often used as an antonym for a loyalist.
He felt like a Brutus after voting against his best friend.
The politician was labeled a Brutus by his former colleagues after he defected to the rival party during the crisis.
From Latin Brutus.
Usage
When used as a common noun to mean 'traitor', it is often capitalized due to its origins as a proper name.