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 the Broncos aren’t just about putting the ball in the back of the net — their defense has allowed just six goals all season and is led by near-impenetrable sophomore goalkeeper Ava de Leest. — Shaun Goodwin, Idaho Statesman, 17 Oct. 2026

Cue an enthralling chase sequence, doubling back through those higgledy-piggledy Portland streetscapes, toward the woods — the impenetrable thickets and thorns of which magically part in her presence. — Guy Lodge, Variety, 11 Oct. 2026

Medical bills are often impenetrable documents littered with complex codes and terminology, and sorting through charges and details about insurance coverage can feel intimidating, if not downright paralyzing. — Jennifer Schlinger, The Conversation, 6 Oct. 2026

The San Juans are among the most impenetrable mountains in the West. — Peter Hessler, New Yorker, 28 Sep. 2026