A person who uses obscenities, vulgarities, or profanities in their speech, especially at inappropriate times. Used especially in reference to a child or as a childish rebuke to an adult. Hey, you little potty 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 potty mouth about it, Rick. You could have just said no like a civilized person.