unbuckle

verb (used without object), un·buck·led, un·buck·ling.

1. to unfasten the buckle or buckles of.

verb (used without object), un·buck·led, un·buck·ling.

2. to undo a buckle.

v.late 14c., from un- (2) “reverse of” + buckle (v.1). Related: Unbuckled; unbuckling.