a flat, typically rectangular frame with a hinged pin, used for joining the ends of a belt or strap

most rucksacks have quick release buckles

a belt buckle

a cake made with fruit (typically blueberries) and having a streusel topping

finish off the meal with a blueberry buckle for dessert

fasten with a buckle

he buckled his belt

bend and give way under a weight or force

the bridge started shaking and then it began to buckle

a weaker person might have buckled under the strain