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 hurt or itch to hear what these cowards have to 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.