76 entries under strong topic. ×

20
inexorable(adjective, characteristic, mean, hard)
19
unyielding(adjective, characteristic, mean, hard)
16
firm(noun, adjective, mean, hard)
16
rigid(adjective, mean, hard, tough)
15
adamant(adjective, mean, hard, strength)
15
stubborn(adjective, characteristic, quality, mean)
14
obdurate(adjective, hard, tough, firm)
14
steel(adjective, hard, strength, tough)
13
inflexible(adjective, mean, hard, tough)
13
hard(noun, adjective, characteristic, mean)
13
relentless(adjective, mean, hard, tough)
12
unbending(adjective, mean, hard, tough)
11
implacable(adjective, mean, hard, tough)
10
adamantine(adjective, set, hard, tough)
8
determined(adjective, hard, tough, firm)
7
indomitable(adjective, characteristic, hard, tough)
7
robust(adjective, hard, tough, inflexible)
6
ferrous(adjective, hard, tough, inflexible)
6
steely(adjective, dull, hard, tough)
6
sturdy
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APASmart Define. (2015). iron thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/iron/thesaurus/synonyms
ChicagoSmart Define. 2015. "iron thesaurus" https://smartdefine.org/iron/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, iron thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/iron/thesaurus/synonyms>.
MLASmart Define. "iron thesaurus" 14 April 2015. Web. 25 September 2026. <https://smartdefine.org/iron/thesaurus/synonyms>