Verb: belt up
Usage: Brit, informal
- [Brit, informal] Refuse to talk or stop talking; fall silent
"The suspect belted up when questioned by the police";
- close up, clam up [informal], dummy up [N. Amer, informal], shut up, button up, be quiet, keep mum [informal]
- Fasten one's seatbelt
"Remember to belt up before driving"
Usage: Brit, informal
- Be quiet, stop talking
- put a sock in it [informal], shut up
Derived forms: belts up, belting up, belted up
Antonym: open up