1. The substitution of a title for a proper name, as in addressing a physician as "Doctor" or a nurse as "Nurse."

use of an epithet for a proper name (or vice versa; as in His Holiness for the name of a pope), 1580s, from Latin, from Greek antonomasia, from antonomazein "to name instead, call by a new name,& [..]

Change of a noun proper into an improper, e.g., Crœsus, for a rich man. Alt, Gr.

the use of a proper name to express a general idea or a substitution of an epithet, or descriptive phrase, or official title for a proper name. "the

Antonomasia is   the use of a proper name to stand for something else having an attribute associated with that name, or the use of a general term to stand for a referent having a proper name.

the substitution of a title or epithet for a proper name. "Yes, Your Majesty." Also, the substitution of a personal name for a common noun. "You're a Benedict Arnold." See [..]

The use of some epithet or the name of some office, dignity, or the like, instead of the proper name of the person; as when his majesty is used for a king, or when, instead of Aristotle, we say, the philosopher; or, conversely, the use of a proper name instead of an appellative, as when a wise man is called a Solomon, or an eminent orator a Cicero. [..]