Meaning

• To distort or collapse under physical pressure; especially, of a slender structure in compression.

• To make bend; to cause to become distorted.

• To give in; to react suddenly or adversely to stress or pressure (of a person).

  "It is amazing that he has never buckled after so many years of doing such urgent work."

• To yield; to give way; to cease opposing.

• To enter upon some labour or contest; to join in close fight; to contend.

• To buckle down; to apply oneself.