noun
Achilles tendon; calcaneal tendon
Anatomical term for the tendon at the back of the ankle.
アキレス腱を切ってしまった。
I tore my Achilles tendon.
noun
Figurative use for a person's or system's most vulnerable spot.
彼のアキレス腱は優しすぎることだ。
His Achilles' heel is that he is too kind.