106 entries under tough topic. ×

1
recalcitrant(firm, unreasonable, grim, obstinate)
1
rough(adjective, strong, hard, severe)
1
sanguinary(adjective, hard, harsh, violent)
1
shameless(adjective, hard, harsh, cruel)
1
sour(adjective, hard, harsh, grim)
1
thick-skinned(adjective, mean, hard, harsh)
1
tyrannical(adjective, hard, evil, nasty)
1
uncontrite(adjective, hard, harsh, cruel)
1
uncooperative(adjective, mean, hard, harsh)
1
unimpressible(adjective, mean, hard, harsh)
1
unregenerate(adjective, hard, harsh, cruel)
1
unrepenting(adjective, hard, harsh, cruel)
1
unshakable(adjective, mean, hard, firm)
0
dense(adjective, strong, hard, sturdy)
0
ferric(adjective, strong, hard, sturdy)
0
ferrous(adjective, strong, hard, sturdy)
0
hard-shell(adjective, strong, hard, severe)
0
hard as nails(expression, adjective, idiom, strong, hard)
0
robust(adjective, strong, hard, sturdy)
0
rock hard(expression, adjective, strong, hard)
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APASmart Define. (2016). implacable thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/implacable/thesaurus/synonyms
ChicagoSmart Define. 2016. "implacable thesaurus" https://smartdefine.org/implacable/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2016, implacable thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/implacable/thesaurus/synonyms>.
MLASmart Define. "implacable thesaurus" 24 March 2016. Web. 22 September 2026. <https://smartdefine.org/implacable/thesaurus/synonyms>