expression, ichidan verb
collapse; give way; lose one's nerve
Idiomatic expression meaning to lose physical strength in the lower body, or figuratively to lose resolve or give up under pressure. Often used when someone's legs buckle or they become unable to stand firm.
See also: 腰砕け (こしくだけ)
あまりの衝撃に腰が砕けて座り込んでしまった。
The shock was so great that my knees gave way and I sank to the ground.
彼は上司に厳しく言われて腰が砕けた。
He lost his nerve when his boss scolded him harshly.