85 entries under hard topic. ×

6
steely(adjective, dull, strong, tough)
5
harsh(adjective, characteristic, mean, tough)
5
immovable(adjective, mean, strong, tough)
5
resolute(adjective, determined, resolution, rigid)
4
cruel(adjective, strong, tough, inflexible)
4
obstinate(adjective, set, mean, strong)
4
pig(noun, metal)
3
dense(adjective, set, strong, tough)
3
heavy(adjective, strong, tough, inflexible)
3
indurate(adjective, set, mean, firm)
3
stiff-necked(adjective, mean, tough, firm)
3
strict(adjective, persistent, rigid, obstinate)
3
tough(adjective, mean, strong, firm)
3
uncooperative(adjective, mean, persistent, rigid)
2
cast(noun, metal)
2
compact(adjective, set, strong, firm)
2
dogged(adjective, mean, strong, tough)
2
ferric(adjective, strong, tough, inflexible)
2
ferrous metal(noun, expression)
2
immutable(adjective, set, stiff, rigid)
11 years ago|13k views|share |citing 
APASmart Define. (2015). iron thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/iron/thesaurus/synonyms
ChicagoSmart Define. 2015. "iron thesaurus" https://smartdefine.org/iron/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2015, iron thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/iron/thesaurus/synonyms>.
MLASmart Define. "iron thesaurus" 14 April 2015. Web. 27 September 2026. <https://smartdefine.org/iron/thesaurus/synonyms>