prim

a. 规规矩矩的,呆板的,拘谨的
v. 弄整齐,地把嘴闭紧

You can't tell that joke to her she's much too prim and proper.

可别给她讲那样的笑话--她这人过於古板和认真.

Prim and sedate.

严肃沉闷的