2
jam-packed(adjective, close, solid, short, substantial)
2
massive
2
opaque
2
packed(adjective, close, solid, short, substantial)
2
resistant(adjective, proof, unaffected, unyielding, unbending)
2
retentive(adjective, tight, proof, impervious, hermetic)
2
serried
2
thickset
2
unpierceable(unaffected, unyielding, unbending, resistant, unreceptive)
2
water-resistant(adjective, impenetrable)
2
water-tight(adjective, tight, proof, impervious, hermetic)
1
air-locked(adjective, tight, proof, impervious, hermetic)
1
air-proof(adjective, tight, proof, impervious, hermetic)
1
airproof(adjective, tight, proof, impervious, hermetic)
1
close-grained(adjective, close, set, hard, tough)
1
close-knit
1
close-textured
1
close-woven
1
coherent
1
cohesive
11 years ago|4.5k views|share |citing 
APASmart Define. (2015). impermeable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/impermeable/thesaurus/synonyms
ChicagoSmart Define. 2015. "impermeable thesaurus" https://smartdefine.org/impermeable/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2015, impermeable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/impermeable/thesaurus/synonyms>.
MLASmart Define. "impermeable thesaurus" 14 April 2015. Web. 23 September 2026. <https://smartdefine.org/impermeable/thesaurus/synonyms>