141 entries under tough topic. ×

1
fixed(adjective, strong, sound, solid)
1
formal(adjective, firm, fixed, distant)
1
hard-boiled(adjective, hard, harsh, indifferent)
1
hard-line(adjective, firm, fixed, rigid)
1
hardboiled(adjective, determined, serious, stiff)
1
hardened(adjective, set, strong, hard)
1
heavy(adjective, strong, hard, sound)
1
heavy-duty(adjective, strong, sound, solid)
1
hold the fort(expression, adjective, idiom, firm)
1
hold the line(expression, adjective, idiom, firm)
1
immovable(adjective, calm, strong, hard, cool)
1
in fine feather(expression, adjective, idiom, strong, sound)
1
incompliant(adjective, firm, fixed, distant)
1
inelastic(adjective, firm, fixed, distant)
1
inexorable(adjective, strong, hard, firm)
1
inflexible(adjective, set, strong, hard)
1
insensitive(adjective, hard, indifferent, cruel)
1
intractable(adjective, firm, fixed, distant)
1
locked in(expression, adjective, firm, distant)
1
muscular(adjective, strong, sound, solid)
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APASmart Define. (2015). hard as nails thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/hard_as_nails/thesaurus/synonyms
ChicagoSmart Define. 2015. "hard as nails thesaurus" https://smartdefine.org/hard_as_nails/thesaurus/synonyms (accessed September 30, 2026).
HarvardSmart Define 2015, hard as nails thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/hard_as_nails/thesaurus/synonyms>.
MLASmart Define. "hard as nails thesaurus" 10 April 2015. Web. 30 September 2026. <https://smartdefine.org/hard_as_nails/thesaurus/synonyms>