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

There was a metal gate rolled out making the front portion of the plane an impenetrable fortress. — David Hookstead Outkick, FOXNews.com, 7 Aug. 2026

Instead, my trembling body was confronted by an impenetrable wall of rock. — Literary Hub, 6 Aug. 2026

The stormy painting conjures the first moments of In the Hand of Dante, as the titular character, portrayed by Oscar Isaac, scales perilously steep steps to what seems an impenetrable stronghold. — A.d. Amorosi, SPIN, 6 Aug. 2026

At a time when Disney’s once-impenetrable Marvel Cinematic Universe has been exhibiting concerning signs of wear and tear at the box office, Spider-Man is getting more and more powerful. — Rebecca Rubin, Variety, 28 July 2026