The term 'Be a Motormouth' refers to someone who talks incessantly. The crossword solutions for this term are YAP (3 letters), BLABBER (7 letters), and YAK (3 letters). YAP is an informal verb meaning to talk rapidly and incessantly, while BLABBER is a verb meaning to talk foolishly or indiscreetly. YAK is also an informal verb meaning to talk at length, often about trivial matters. All three words refer to someone who talks too much.