impenetrable
adjective
im·pen·e·tra·ble (ˌ)im-ˈpe-nə-trə-bəl 
1
a
: incapable of being penetrated or pierced
b
: inaccessible to knowledge, reason, or sympathy : impervious
2
: incapable of being comprehended : inscrutable
impenetrably
(ˌ)im-ˈpe-nə-trə-blē
adverb 
Synonyms
- impassable
- impassible
- impermeable
- impervious
- impregnable
See all Synonyms & Antonyms 
Example Sentences
The fort's defenses were thought to be impenetrable. the ancient temple was surrounded by vast stretches of impenetrable jungle
Recent Examples on the Web Garner all but disappears behind Anna’s thick Russian-German accent and chunky designer glasses, wielding an air of hauteur like an impenetrable shield. 
Angie Han, The Hollywood Reporter, 9 Feb. 2022 Still, his changes provide only a cushion against sanctions, not an impenetrable shield. New York Times, 3 Feb. 2022 If the last few days have reminded us of anything, it’s that the COVID pandemic is far from over, and being fully vaccinated does not give someone an impenetrable shield. Nancy Armour, USA TODAY, 20 July 2021 The vaccines, though effective, do not form an impenetrable shield against the virus. Compiled Democrat-gazette Staff From Wire Reports, Arkansas Online, 18 July 2021 The vaccines, though marvels of basic and applied science, do not form an impenetrable shield against SARS-CoV-2. BostonGlobe.com, 18 July 2021 The vaccines, though marvels of basic and applied science, do not form an impenetrable shield against SARS-CoV-2. Joel Achenbach, Anchorage Daily News, 17 July 2021 The vaccines, though marvels of basic and applied science, do not form an impenetrable shield against SARS-CoV-2. Joel Achenbach, Star Tribune, 17 July 2021 Yet as warming winters bring abnormal rain, caribou grazing areas are being coated by an impenetrable armor of ice, altering their migration patterns. Jon Waterman, Outside Online, 15 June 2020 See More
Angie Han, The Hollywood Reporter, 9 Feb. 2022 Still, his changes provide only a cushion against sanctions, not an impenetrable shield. New York Times, 3 Feb. 2022 If the last few days have reminded us of anything, it’s that the COVID pandemic is far from over, and being fully vaccinated does not give someone an impenetrable shield. Nancy Armour, USA TODAY, 20 July 2021 The vaccines, though effective, do not form an impenetrable shield against the virus. Compiled Democrat-gazette Staff From Wire Reports, Arkansas Online, 18 July 2021 The vaccines, though marvels of basic and applied science, do not form an impenetrable shield against SARS-CoV-2. BostonGlobe.com, 18 July 2021 The vaccines, though marvels of basic and applied science, do not form an impenetrable shield against SARS-CoV-2. Joel Achenbach, Anchorage Daily News, 17 July 2021 The vaccines, though marvels of basic and applied science, do not form an impenetrable shield against SARS-CoV-2. Joel Achenbach, Star Tribune, 17 July 2021 Yet as warming winters bring abnormal rain, caribou grazing areas are being coated by an impenetrable armor of ice, altering their migration patterns. Jon Waterman, Outside Online, 15 June 2020 See More Word History
Etymology
Middle English impenetrabel, from Middle French impenetrable, from Latin impenetrabilis, from in- + penetrabilis penetrable
First Known Use
15th century, in the meaning defined at sense 1a
Kids Definition
impenetrable
adjective
im·pen·e·tra·ble im-ˈpe-nə-trə-bəl
1
: impossible to pass through or see through
impenetrable walls
impenetrable darkness
2
: impossible to understand
an impenetrable mystery
impenetrable
adjective
1
as in dense
impossible to get through or into the ancient temple was surrounded by vast stretches of impenetrable jungle Synonyms & Similar Words
Relevance
- dense
- impervious
- impregnable
- thick
- impermeable
- impassable
- close
- sturdy
- impassible
- tight
- compact
- solid
- substantial
- compressed
- frozen
- tough
- condensed
- rigid
- hard
- inflexible
- unyielding
- stiff
- firm
- unbending
Antonyms & Near Antonyms
- permeable
- soft
- passable
- penetrable
- negotiable
- elastic
- flexible
- giving
- malleable
- porous
- pliable
- yielding
- squishy
- absorbent
- bendable
2
as in mysterious
being beyond one's powers to know, understand, or explain the mysteries of that religion are completely impenetrable to outsiders Synonyms & Similar Words
- mysterious
- cryptic
- obscure
- enigmatic
- inscrutable
- mystic
- uncanny
- deep
- dark
- murky
- arcane
- enigmatical
- occult
- ambiguous
- unexplainable
- mystical
- confusing
- vague
- incomprehensible
- unintelligible
- esoteric
- unfathomable
- shadowy
- fuzzy
- inexplicable
- metaphysical
- unknowable
- darkling
- imponderable
- abstruse
- unanswerable
- unaccountable
- baffling
- bewildering
- recondite
- mystifying
- perplexing
- supernatural
- confounding
- befuddling
- unsearchable
- equivocal
- puzzling
- disorienting
- numinous
Antonyms & Near Antonyms
- intelligible
- understandable
- transparent
- fathomable
- clear
- plain
- obvious
- apparent
- straightforward
- unambiguous
- unmistakable
- evident
- palpable
- unequivocal
- perspicuous
- manifest
- patent
- open-and-shut
3
as in incomprehensible
impossible to understand the textbook's language is completely impenetrable, at least to me Synonyms & Similar Words
- incomprehensible
- unintelligible
- mysterious
- unfathomable
- ungraspable
- obscure
- esoteric
- confusing
- inscrutable
- cryptic
- uncanny
- indecipherable
- enigmatic
- abstruse
- recondite
- mystic
- baffling
- deep
- unknowable
- bewildering
- perplexing
- puzzling
- mystifying
- unanswerable
- oblique
- confounding
- enigmatical
- unsearchable
- darkling
- inconceivable
- occult
- unimaginable
- unthinkable
Antonyms & Near Antonyms
- intelligible
- understandable
- essential
- basic
- underlying
- fundamental
- rudimentary
- elementary
- easy
- elemental
- simple
- fathomable
- coherent
- systematic
- clear
- connected
- plain
- orderly
- compelling
- straightforward
- convincing
- organized
- cogent
- lucid
- systematized
- ordered
- pellucid
- perspicuous
4
as in impermeable
not allowing penetration (as by gas, liquid, or light) the container of toxic waste has an impenetrable seal to prevent leaks Synonyms & Similar Words
- impermeable
- impervious
- tight
- thick
- dense
- close
- hermetic
- airtight
- watertight
- compact
- snug
- leakproof
- lightproof
- soundproof
- hermetical
- waterproof
Antonyms & Near Antonyms
- permeable
- penetrable
- porous
- pervious
- leaky
- absorbent
- unsealed