/ əˌkɪliːz ˈhiːl; NAmE / noun
[ sing. ] a weak point or fault in sb's character, which can be attacked by other people
ORIGIN: Named after the Greek hero Achilles . When he was a small child, his mother held him below the surface of the river Styx to protect him against any injury. She held him by his heel, which therefore was not touched by the water. Achilles died after being wounded by an arrow in the heel.