belt up vs open up

To stop talking or chattering; to shut up. 

To fasten one's seat belt. 

Synonym of cheat out (“to face or turn toward the audience more than would be natural”) 

To begin running, driving, travelling, etc., at maximum speed. 

To commence firing weapons. 

To rain. 

To open. 

To widen. 

To reveal oneself; to share personal information about oneself; to become communicative.