Definition of as hard as nails
- He's as hard as nails.
: not easily penetrated : not easily yielding to pressure
: not capable of being spread : very firm
: having a harsh or acid taste
: with great or utmost effort or energy : strenuously
: in a violent manner : fiercely
: to the full extent
What made you want to look up as hard as nails? Please tell us where you read or heard it (including the quote, if possible).