Verb
(transitive) To fasten with a buckle.
(intransitive, idiomatic) To fasten one's seat belt or safety belt.
Synonym: belt up
Buckle up every time you drive somewhere in a car, and make sure your passengers buckle up, too.
And as it turns out, if one person is praying for you, buckle up. Things can happen. Anne Lamott
One of those has been the responsibility of keeping the Buckle Up for Lane Memorial Tournament running. Source: Internet