look as if butter wouldn't melt in your mouth

look as if butter wouldn't melt in (one's) mouth

To appear innocent or reserved in certain company, when in fact one may have the opposite demeanor. Sure, he looks as if butter wouldn't melt in his mouth when he's around people he doesn't know, but stay a while and you'll see what he's really like.See also: butter, if, look, melt, mouth

look as if butter wouldn't melt in your mouth

appear deceptively gentle or innocent. informalSee also: butter, if, look, melt, mouth