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shell; husk; hull; pod; chaff
「殻」 has other readings with different meanings.
卵の殻をきれいに剥いて料理した。
I peeled the eggshell cleanly.
貝の殻を海辺で集めるのが趣味だ。
Collecting seashells is my hobby.
彼は自分の殻に閉じこもった。
He withdrew into his shell.