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.
In my opinion, it means that correct and polite behavior in society (âmannersâ) are what distinguish us (âmanâ) from beasts or mere animals. In the movie, it highlights the fact that without manners, you are no different than a wild animal (context: the Kingsman addresses the ruffians).