61 entries under persistent topic. ×

11
hard(adjective, mean, strong, tough, severe)
11
pitiless(adjective, animal, mean, hard, tough)
10
iron(adjective, mean, strong, hard, tough)
9
obstinate(adjective, mean, hard, cruel, determined)
8
inhuman(adjective, animal, mean, hard, tough)
8
mortal(adjective, mean, severe, harsh, cruel)
8
vindictive(adjective, mean, hard, tough, severe)
7
determined(adjective, strong, hard, tough, harsh)
7
dogged(adjective, appearance, mean, hard, tough)
7
stiff-necked(adjective, mean, strong, hard, tough)
6
incompliant(adjective, resist, determined, resolute)
6
tough(adjective, mean, strong, hard, firm)
6
unflinching(adjective, mean, severe, harsh, cruel)
5
brassbound(adjective, resist, determined, resolute)
5
die-hard(adjective, resist, determined, resolute)
5
ferocious(adjective, animal, mean, evil, nasty)
5
unbendable(adjective, resist, determined, resolute)
4
bullheaded(adjective, strong, hard, tough, firm)
4
mulish(adjective, mean, strong, hard, tough)
4
stiff(adjective, harsh, cruel, determined, fierce)
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APASmart Define. (2016). implacable thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/implacable/thesaurus/synonyms
ChicagoSmart Define. 2016. "implacable thesaurus" https://smartdefine.org/implacable/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2016, implacable thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/implacable/thesaurus/synonyms>.
MLASmart Define. "implacable thesaurus" 24 March 2016. Web. 21 September 2026. <https://smartdefine.org/implacable/thesaurus/synonyms>