belt up

verb (adverb)

(slang) to become or cause to become silent; stop talking: often used in the imperative

to fasten with or by a belt, esp a seat belt

Slang definitions & phrases for belt up

verb phrase

To hold one's peace; be quiet; shut up: Maybe he can get Pauline Kael to belt up once in a while (chiefly British 1930s+ air force)