Full Definition of EPITHET. 1. a: a characterizing word or phrase accompanying or occurring in place of the name of a person or thing b: a disparaging or abusive word or phrase c: the part of a taxonomic name identifying a subordinate unit within a genus.2. obsolete: expression.. a: a characterizing word or phrase accompanying or occurring in place of the name of a person or thing b: a disparaging or abusive word or phrase c: the part of a taxonomic name identifying a subordinate unit within a genus. 2. obsolete: expression.