Coward
noun
You learned that 抜ける is "to fall out." If your waist falls out, you can't remain standing. You have to curl up on the ground, like a coward.
This word uses the kun'yomi readings for both kanji, which you've learned already. Go you!
私は腰抜けだから言い返したくても言い返せないの。
I am such a coward, so I can't talk back even if I wanted to.
次にオレを腰抜けと呼んだら、許さないぞ！
The next time you call me a coward, I will not forgive you!
腰抜け共に何を言われても痛くもかゆくもないよ。
It doesn't bother me one bit what those cowards say.
管理職に昇進する前に辞職する腰抜け社員が多すぎる。
There are too many coward employees who resign before being promoted to management.