Definitions
1.verbTo distort or collapse under physical pressure; especially, of a slender structure in compression.
2.verbTo make bend; to cause to become distorted.
3.verbTo 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."
4.verbTo yield; to give way; to cease opposing.
5.verbTo enter upon some labour or contest; to join in close fight; to contend.
6.verbTo buckle down; to apply oneself.