Nouns

(n)bucklefastener that fastens together two ends of a belt or strap; often has loose prong
(n)warp, bucklea shape distorted by twisting or folding

Verbs

(v)buckle, claspfasten with a buckle or buckles
(v)buckle, crumplefold or collapse“His knees buckled”
(v)heave, buckle, warpbend out of shape, as under pressure or from heat“The highway buckled during the heat wave”