The definition of an adjective is a part of speech that is used to describe a noun. Red, tall, better and fast are all examples of adjectives.
In modern parlance, a gentleman (from gentle + man, translating the Old French gentilz hom) is any man of good, courteous conduct. A gentleman may also simply be a polite term for any man, as in indications of gender-separated facilities, or as a sign of the speaker's own courtesy when addressing others. The modern female equivalent is lady.
For the racehorse, see Gentilhombre (horse). In modern parlance, the term gentleman (from Latin gentis, belonging to a race or gens, and man, the Italian gentil uomo or gentiluomo, the French gentilhomme, the Spanish gentilhombre, the Portuguese gentil-homem , and the Esperanto gentilmano) refers to any man of good, courteous conduct.