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.
gentlemen, (used as a form of address): Gentlemen, please come this way. a civilized, educated, sensitive, or well-mannered man: He behaved like a true gentleman. a male personal servant, especially of a man of social position; valet.