1
adamantean
1
at a standstill(expression, idiom)
1
atomic number 6
1
austere(adjective, strong, hard, tough, severe)
1
authoritarian(adjective, strong, hard, tough, sturdy)
1
bulky
1
callous(adjective, set, strong, hard, firm)
1
certain
1
corneous
1
dead set(adjective, determined, resolute, uncompromising, unshakeable)
1
demanding
1
diamond
1
diamond-like
1
difficult
1
dour
1
dyed-in-the-wool(adjective, set, strong, hard, tough)
1
enduring
1
frozen
1
granitic
1
hard-hearted
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APASmart Define. (2015). adamantine thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/adamantine/thesaurus/synonyms
ChicagoSmart Define. 2015. "adamantine thesaurus" https://smartdefine.org/adamantine/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2015, adamantine thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/adamantine/thesaurus/synonyms>.
MLASmart Define. "adamantine thesaurus" 10 April 2015. Web. 23 September 2026. <https://smartdefine.org/adamantine/thesaurus/synonyms>