(of a person) very correctly behaved and easily shocked by anything that is rude: Don't invite her to the party. She's so prim and proper.

What does being prim and proper mean?

/prɪm/ primmer | primmest. very formal and correct in behavior and easily shocked by anything rude: She's much too prim and proper to drink pints of beer. Synonyms.

Is prim and proper an idiom?

Meaning: Someone who is prim and proper always behaves in the correct way and never breaks the rules of etiquette. ... Idiom Definition.