hard as iron
Proposed by a contributor, not yet supported by evidence.
Meaning · English
very hard
Where it’s used:
Used
American English
Examples
The Torah notes that a teacher of the law must be as hard as iron.
Usage example from English Wiktionary (CC BY-SA 4.0, retrieved 2026-07-30)
Sources & notes
Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-07-30 via kaikki.org).
Common questions
What does “hard as iron” mean?
very hard
Is “hard as iron” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.