noun which may take the genitive case particle 'no', na-adjective, noun
Describes a person or behavior that lacks proper manners or etiquette. Often used as a criticism.
彼は礼儀知らずな態度をとった。
He took a rude attitude.
そんなことを言うなんて礼儀知らずだ。
It's impolite to say such a thing.