1
puissant(adjective, strength)
1
recalcitrant(tough, firm, unreasonable, grim, obstinate)
1
rock
1
rock-ribbed(adjective, determined, resolute, uncompromising, unshakeable)
1
single-minded(tough, firm, cruel, stiff, strict)
1
sound
1
stable
1
standpat
1
stationary
1
staunch(hard, resolute, rigid, inflexible, strict)
1
stony-hearted
1
stringent(adjective, hard, severe, stiff, resolute)
1
strong-willed(adjective, determined, resolute, uncompromising, unshakeable)
1
stubborn as a mule(adjective, idiom, resist, firmly)
1
sure
1
thick(adjective, strong, hard, tough, firm)
1
unaffected
1
unalterable
1
unchanging
1
ungiving
11 years ago|6.5k views|share |citing 
APASmart Define. (2015). adamantine thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/adamantine/thesaurus/synonyms
ChicagoSmart Define. 2015. "adamantine thesaurus" https://smartdefine.org/adamantine/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, adamantine thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/adamantine/thesaurus/synonyms>.
MLASmart Define. "adamantine thesaurus" 10 April 2015. Web. 24 September 2026. <https://smartdefine.org/adamantine/thesaurus/synonyms>