v.1. To bend, crumple or collapse under some great weight or pressure: The bridge supports were weakened by rust and buckled under the weight of the heavy truck. The metal chair I was sitting on suddenly buckled under, and I fell to the ground.
2. To succumb to or be adversely affected by some pressure: Some schools have buckled under the strain of having too many new students. I had fought very hard against their ideas but finally buckled under to them.