butter wouldn't melt in someone's mouth
idiomPart ofbutter
butter wouldn't melt in someone's mouth — idiom
1. looking sweet and innocent, while actually being naughty or willing to cause tro
1.idiom
Definition
looking sweet and innocent, while actually being naughty or willing to cause trouble.
Example
Little Mia stares at the broken vase as if butter wouldn't melt in her mouth.
The boss seems polite at meetings, but butter wouldn't melt in his mouth.