any word or phrase applied to a person or thing to describe an actual or attributed quality

Richard the Lion-Hearted is an epithet of Richard I.

a characterizing word or phrase firmly associated with a person or thing and often used in place of an actual name, title, or the like, as man's best friend for dog.

a word, phrase, or expression used invectively as a term of abuse or contempt, to express hostility, etc.

noun

appellation , description , designation , name , sobriquet , tag , titlenotes:an epitaph is an inscription on a tombstone or monument in memory of the person buried there , while an epithet is a defamatory or abusive word or phrase , appellative , cognomen , denomination , nickname , style , title , blasphemy , curse , expletive , oath , insult , label , phrase , term