watch one's mouth in Portuguese

(idiomatic, US) To be careful about what one says, especially with regard to disrespectful or profane language.

(idiomatic, US) To be careful about what one says, especially with regard to disrespectful or profane language.

(idiomatic, chiefly, US) In the imperative form, used as a warning to choose one's words carefully or else be silent, for fear of consequences.