Refers to a lack of decorum or propriety in speech.
El deslengua del personaje principal lo llevó a meterse en problemas, ya que no pensaba antes de hablar.
The main character's lack of restraint led him to get into trouble, as he did not think before speaking.
Su deslengua en la reunión sorprendió a todos, ya que no esperaba que hablara de esa manera.
His lack of restraint in the meeting surprised everyone, as they did not expect him to speak that way.