Even though it's not improper or vulgar, I'm not sure how often you want to use this word around Mom... Nonetheless, here it is:
A prig is someone who displays or demands pointlessly precise conformity, fussiness about trivialities, or exaggerated propriety, especially in a self-righteous or irritating manner. Not to be confused with a similar sounding word that means "an obnoxious or contemptible person", but is considered vulgar.
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