Achilles heel

Or Achilles' heel

noun

1. a portion, spot, area, or the like, that is especially or solely vulnerable.

   His Achilles heel is his quick temper.

Achilles heel

noun

1. a small but fatal weakness

Achilles' heel

1. A point of vulnerability. (See Achilles.)

Word History and Origins

Origin of Achilles heel¹

First recorded in 1800–10

Idioms and Phrases

A fatal weakness, a vulnerable area, as in This division, which is rarely profitable, is the company's Achilles' heel. The term alludes to the Greek legend about the heroic warrior Achilles whose mother tried to make him immortal by holding the infant by his heel and dipping him into the River Styx. Eventually he was killed by an arrow shot into his undipped heel. [c. 1800]