toilet mouth
A person who uses obscenities, vulgarities, or profanities in his or her speech, especially at inappropriate times. Used especially in reference to a child or as a childish rebuke to an adult. Hey, you little toilet mouth! If I hear you speaking like that around your grandmother again, you're going to be grounded for a week! Well there's no need to be a toilet mouth about it, Rick. You could have refused like a civilized person.