v (intransitive) To distort or collapse under physical pressure; especially, of a slender structure in compression.
v (intransitive|figuratively) To give in; to react suddenly or adversely to stress or pressure (of a person).
n (countable) A clasp used for fastening two things together, such as the ends of a belt, or for retaining the end of a strap.
n (context|roofing) An upward, elongated displacement of a roof membrane frequently occurring over insulation or deck joints. A buckle may be an indication of movement with the roof assembly.