noun
prim person; prude; stuck-up person
Describes someone who acts overly proper, reserved, or self-consciously refined, often with a hint of disapproval.
彼女は澄まし屋で、いつも上品ぶっている。
She's a prim person, always putting on airs of refinement.
あの澄まし屋には話しかけにくい。
That stuck-up person is hard to talk to.
The verb form meaning 'to clear' or 'to put on airs'; 澄まし屋 is derived from the 'put on airs' sense.
A prim or composed facial expression, often used for someone trying to look refined.
From the verb 澄ます (to put on airs) + 屋 (person with a certain trait).