Mouth off is an idiom that means to speak out boldly and without fear of consequences. The crossword solutions for this term are SASS (4 letters), RAVE (4 letters), YAP (3 letters), RANT (4 letters), and GETWISE (7 letters). SASS is an acronym for 'sarcastic attitude and smart remarks', and it is used to describe someone who speaks in a sarcastic or witty manner. RAVE is a verb meaning to talk enthusiastically and at length about something. YAP is a verb meaning to talk incessantly and often in a high-pitched voice. RANT is a verb meaning to speak or shout angrily and at length. Finally, GETWISE is a verb meaning to become wise or knowledgeable.