腰こしが抜ぬける

expression, ichidan verb

be unable to stand; be weak in the knees; be paralyzed with fear; be dumbfounded

Describes a state where one's legs give out, often from shock, fear, or extreme surprise. Can be literal (physical weakness) or figurative (stunned).

• あまりの恐きょう怖ふに腰こしが抜ぬけて立たてなかった。

  I was so terrified that my legs gave out and I couldn't stand.

• 突とつ然ぜんの知しらせに腰こしが抜ぬけるほど驚おどろいた。

  I was so shocked by the sudden news that I felt weak in the knees.