35 entries under firm topic. ×

30
indestructible(adjective, strong, tough, rigid)
23
tough(adjective, strong, solid, stiff)
20
adamantine(adjective, strong, tough, severe)
19
rock-hard(adjective, rigid, unyielding, steely)
18
flinty(adjective, strong, hard, solid)
18
impenetrable(adjective, solid, stiff, rigid)
9
unyielding(adjective, strong, hard, tough, severe)
8
rigid(adjective, strong, hard, severe)
6
steely(adjective, rigid, unyielding)
5
solid(adjective, strong, hard, tough, severe)
5
hard(adjective, strong, severe, harsh)
5
adamant(adjective, rigid, unyielding, steely)
5
rocky(adjective, stiff, rigid, unyielding)
4
durable(adjective, strong, hard, tough)
4
stony(adjective, stiff, rigid, unyielding)
3
strong(adjective, hard, solid, stiff)
2
harsh(adjective, severe, solid, stiff)
2
stiff(adjective, strong, hard, severe)
1
definite(adjective, severe, harsh, solid)
1
inflexible(adjective, strong, hard, severe)
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APASmart Define. (2016). unbreakable thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/unbreakable/thesaurus/synonyms
ChicagoSmart Define. 2016. "unbreakable thesaurus" https://smartdefine.org/unbreakable/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2016, unbreakable thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/unbreakable/thesaurus/synonyms>.
MLASmart Define. "unbreakable thesaurus" 5 January 2016. Web. 25 September 2026. <https://smartdefine.org/unbreakable/thesaurus/synonyms>