Synonyms of impenetrable

impenetrable

adjective

(ˌ)im-ˈpe-nə-trə-bəl 

1

as in dense

impossible to get through or into

the ancient temple was surrounded by vast stretches of impenetrable jungle

Synonyms & Similar Words

• dense
• impervious
• close
• impregnable
• impassable
• impermeable
• thick
• frozen
• sturdy
• compact
• tight
• compressed
• substantial
• solid
• tough
• rigid
• hard
• condensed
• inflexible
• stiff
• unyielding
• firm
• unbending

Antonyms & Near Antonyms

• permeable
• soft
• negotiable
• passable
• penetrable
• flexible
• elastic
• 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
• enigmatic
• uncanny
• mystic
• obscure
• deep
• dark
• inscrutable
• murky
• unexplainable
• ambiguous
• arcane
• vague
• confusing
• mystical
• occult
• incomprehensible
• fuzzy
• unintelligible
• esoteric
• metaphysical
• shadowy
• unfathomable
• inexplicable
• darkling
• unknowable
• supernatural
• unaccountable
• imponderable
• unanswerable
• equivocal
• unsearchable
• abstruse
• baffling
• perplexing
• recondite
• puzzling
• confounding
• numinous
• disorienting
• mystifying
• bewildering
• befuddling

Antonyms & Near Antonyms

• intelligible
• understandable
• clear
• obvious
• transparent
• apparent
• plain
• evident
• fathomable
• unmistakable
• unambiguous
• straightforward
• manifest
• palpable
• unequivocal
• perspicuous
• open-and-shut
• patent

3

as in incomprehensible

impossible to understand

the textbook's language is completely impenetrable, at least to me

Synonyms & Similar Words

• incomprehensible
• mysterious
• unintelligible
• unfathomable
• confusing
• uncanny
• esoteric
• obscure
• cryptic
• ungraspable
• inscrutable
• enigmatic
• mystic
• deep
• abstruse
• recondite
• baffling
• puzzling
• indecipherable
• oblique
• unknowable
• perplexing
• unanswerable
• confounding
• inconceivable
• unsearchable
• darkling
• bewildering
• unthinkable
• unimaginable
• mystifying
• occult

Antonyms & Near Antonyms

• intelligible
• understandable
• basic
• essential
• fundamental
• underlying
• elementary
• rudimentary
• easy
• elemental
• simple
• fathomable
• systematic
• coherent
• clear
• connected
• orderly
• plain
• compelling
• organized
• convincing
• straightforward
• cogent
• lucid
• ordered
• systematized
• pellucid
• perspicuous

4

as in tight

not allowing penetration (as by gas, liquid, or light)

the container of toxic waste has an impenetrable seal to prevent leaks

Synonyms & Similar Words

• tight
• impermeable
• thick
• impervious
• dense
• close
• compact
• hermetic
• watertight
• airtight
• leakproof
• snug
• waterproof
• soundproof
• lightproof

Antonyms & Near Antonyms

• permeable
• porous
• pervious
• penetrable
• leaky
• absorbent
• unsealed

Example Sentences

Recent Examples of impenetrable

But even with the Bills having the near-consensus best quarterback in football, this Buffalo team isn't impenetrable, and the Lions have plenty of big-time road experience that could lead to an early-season upset. — Christian Romo, Freep.com, 17 Sep. 2026

For most of our history as a country, and certainly in the post-World War II nuclear era, our borders felt impenetrable. — Michael Silver, New York Times, 11 Sep. 2026

Child safety experts lauded the settlement and the accompanying pressure campaign as a giant leap forward in the effort to regulate an industry that until this year appeared all but impenetrable to reform, either from the courts or legislatures. — Sonja Sharp, Los Angeles Times, 29 Aug. 2026

The space offers guests a rare glimpse into a facet of Japanese nightlife that can feel impenetrable to outsiders. — Condé Nast, Condé Nast Traveler, 26 Aug. 2026