4
everlasting(adjective, strong, tough)
4
durable(adjective, strong, hard, tough, firm)
4
stony(adjective, firm, stiff, rigid, unyielding)
4
lasting(adjective, strong, tough)
4
eternal
4
unshakable(adjective, strong, tough)
3
inviolable(adjective, indestructible)
3
permanent
3
strong(adjective, hard, firm, solid, stiff)
2
armored(adjective, strong, tough)
2
brass-bound(adjective, strong, tough)
2
endless
2
good
2
harsh(adjective, severe, firm, solid, stiff)
2
imperishable
2
indissoluble
2
indivisible(adjective, tenacity, indissoluble)
2
nonbreakable(adjective, strong, tough)
2
real
2
secure(adjective, strengthened, reinforced)
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APASmart Define. (2016). unbreakable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/unbreakable/thesaurus/synonyms
ChicagoSmart Define. 2016. "unbreakable thesaurus" https://smartdefine.org/unbreakable/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2016, unbreakable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/unbreakable/thesaurus/synonyms>.
MLASmart Define. "unbreakable thesaurus" 5 January 2016. Web. 23 September 2026. <https://smartdefine.org/unbreakable/thesaurus/synonyms>