achilles' heel

1. 1.

   a seemingly small but actual mortal weakness

   Broaderweak part

Questions about achilles' heel

What does achilles' heel mean?

achilles' heel means "a seemingly small but actual mortal weakness".

Is achilles' heel a common word?

achilles' heel is banded "Rare" — specialist or archaic — most readers will not have met it. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.