15
hermetic(verb, adjective, tight, proof, closed)
10
sealed(adjective, tight, proof, impervious, hermetic)
9
tight(adjective, proof, impervious, hermetic, sealed)
9
watertight(adjective, tight, proof, impervious, hermetic)
8
air-tight(adjective, tight, proof, impervious, hermetic)
7
closed(verb, adjective, closed, enclosed, sealed)
7
impermeable(adjective, tight, proof, impervious, impenetrable)
7
impervious(adjective, fast, short, tight, dense)
7
unassailable(adjective, certain, indisputable)
7
waterproof(adjective, water, tight, proof, impervious)
5
gas-tight(adjective, tight, proof, impervious, hermetic)
5
irrefutable(adjective, certain, indisputable)
4
airproof(adjective, tight, proof, impervious, hermetic)
4
hermetical(adjective, tight, proof, impervious, hermetic)
4
impenetrable(adjective, sealed)
4
incontrovertible
4
snug
3
certain(adjective, strong, sound, indisputable)
3
dampproof(adjective, tight, proof, impervious, hermetic)
3
fast
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APASmart Define. (2015). airtight thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/airtight/thesaurus/synonyms
ChicagoSmart Define. 2015. "airtight thesaurus" https://smartdefine.org/airtight/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, airtight thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/airtight/thesaurus/synonyms>.
MLASmart Define. "airtight thesaurus" 14 April 2015. Web. 21 September 2026. <https://smartdefine.org/airtight/thesaurus/synonyms>