1. impenetrable(a = adj.all) - not admitting of penetration or passage into or through; "an impenetrable fortress"; "impenetrable rain forests"
Antonym: penetrable
Derived form noun impenetrability1
2. impenetrable(s = adj.all) dense, heavy - permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom"
3. impenetrable(s = adj.all) - impossible to understand; "impenetrable jargon"
Derived form noun impenetrableness1
1. Incapable of being penetrated or pierced; not admitting the passage of other bodies; not to be entered; impervious; as, an impenetrable shield. [1913 Webster]
"Highest woods impenetrable
To star or sunlight." [1913 Webster]
2. Having the property of preventing any other substance from occupying the same space at the same time. [1913 Webster]
3. Inaccessible, as to knowledge, reason, sympathy, etc.; unimpressible; not to be moved by arguments or motives; as, an impenetrable mind, or heart. [1913 Webster]
"They will be credulous in all affairs of life, but impenetrable by a sermon of the gospel." [1913 Webster]
impenetrable, adj.
1 that cannot be penetrated.
2 inscrutable, unfathomable.
3 inaccessible to ideas, influences, etc.
4 Physics (of matter) having the property such that a body is incapable of occupying the same place as another body at the same time.
Derivative:
impenetrability n. impenetrableness n. impenetrably adv.
Etymology:
ME f. F imp{eacute}n{eacute}trable f. L impenetrabilis (as IN-(1), PENETRATE)
N safety, security, surety, impregnability, invulnerability, invulnerableness, danger past, danger over, storm blown over, coast clear, escape, means of escape, blow valve, safety valve, release valve, sniffing valve, safeguard, palladium, guardianship, wardship, wardenship, tutelage, custody, safekeeping, preservation, protection, auspices, safe-conduct, escort, convoy, guard, shield, guardian angel, tutelary god, tutelary deity, tutelary saint, genius loci, protector, guardian, warden, warder, preserver, custodian, duenna, chaperon, third person, watchdog, bandog, Cerberus, watchman, patrolman, policeman, cop, dick, fuzz, smokey, peeler, zarp, sentinel, sentry, scout, garrison, guardship, refuge &c, anchor, precaution, quarantine, cordon sanitaire, confidence, protect, take care of, preserve, cover, screen, shelter, shroud, flank, ward, guard, secure, entrench, intrench, fence round, house, nestle, ensconce, take charge of, escort, convoy, garrison, watch, mount guard, patrol, make assurance doubly sure, take up a loose thread, take precautions, double reef topsails, seek safety, take shelter, find shelter, Adj, safe, secure, sure, in safety, in security, on the safe side, under the shield of, under the shade of, under the wing of, under the shadow of one's wing, under cover, under lock and key, out of danger, out of the woods, out of the meshes, out of harm's way, unharmed, unscathed, on sure ground, at anchor, high and dry, above water, unthreatened, unmolested, protected, cavendo tutus, panoplied, snug, seaworthy, weatherproof, waterproof, fireproof, defensible, tenable, proof against, invulnerable, unassailable, unattackable, impenetrable, impregnable, imperdible, inexpugnable, Achillean, safe and sound, scathless, unhazarded, not dangerous, unthreatening, harmless, friendly (cooperative), protecting, protective, guardian, tutelary, preservative, trustworthy, ex abundanti cautela, with impunity, all's well, salva res est, suave mari magno, a couvert, e terra alterius spectare laborem, Dieu vous garde.
N closure, occlusion, blockade, shutting up, obstruction, embolus, contraction, infarction, constipation, obstipation, blind alley, blind corner, keddah, cul-de-sac, caecum, imperforation, imperviousness, impermeability, stopper, closed, shut, operculated, unopened, unpierced, imporous, caecal, closable, imperforate, impervious, impermeable, impenetrable, impassable, unpassable, invious, pathless, wayless, untrodden, untrod, unventilated, air tight, water tight, hermetically sealed, tight, snug.
N density, solidity, solidness, impenetrability, impermeability, incompressibility, imporosity, cohesion, constipation, consistence, spissitude, specific gravity, hydrometer, areometer, condensation, caseation, solidation, solidification, consolidation, concretion, coagulation, petrification, crystallization, precipitation, deposit, precipitate, inspissation, gelation, thickening, indivisibility, indiscerptibility, insolubility, indissolvableness, solid body, mass, block, knot, lump, concretion, concrete, conglomerate, cake, clot, stone, curd, coagulum, bone, gristle, cartilage, casein, crassamentum, legumin, superdense matter, condensed states of matter, dwarf star, neutron star, dense, solid, solidified, caseous, pukka, coherent, cohesive, compact, close, serried, thickset, substantial, massive, lumpish, impenetrable, impermeable, nonporous, imporous, incompressible, constipated, concrete, knotted, knotty, gnarled, crystalline, crystallizable, thick, grumous, stuffy, undissolved, unmelted, unliquefied, unthawed, indivisible, indiscerptible, infrangible, indissolvable, indissoluble, insoluble, infusible.
N unintelligibility, incomprehensibility, imperspicuity, inconceivableness, vagueness, obscurity, ambiguity, doubtful meaning, uncertainty, perplexity, spinosity, obscurum per obscurius, mystification, latency, transcendentalism, paradox, oxymoron, riddle, enigma, puzzle, diagnus vindice nodus, sealed book, steganography, freemasonry, pons asinorum, asses' bridge, high Dutch, Greek, Hebrew, jargon, unintelligible, unaccountable, undecipherable, undiscoverable, unknowable, unfathomable, incognizable, inexplicable, inscrutable, inapprehensible, incomprehensible, insolvable, insoluble, impenetrable, illegible, as Greek to one, unexplained, paradoxical, enigmatic, enigmatical, puzzling (secret), indecipherable, obscure, dark, muddy, clear as mud, seen through a mist, dim, nebulous, shrouded in mystery, opaque, dense, undiscernible, misty, hidden, latent, indefinite, garbled, perplexed, undetermined, vague, loose, ambiguous, mysterious, mystic, mystical, acroamatic, acroamatical, metempirical, transcendental, occult, recondite, abstruse, crabbed, inconceivable, inconceptible, searchless, above comprehension, beyond comprehension, past comprehension, beyond one's depth, unconceived, inexpressible, undefinable, incommunicable, unpredictable, unforeseeable, it's Greek to me.
N latency, implication, latency, inexpression, hidden meaning, occult meaning, occultness, mystery, cabala, anagoge, silence, concealment, more than meets the eye, more than meets the ear, Delphic oracle, le dessous des cartes, undercurrent, implication, logical implication, logical consequence, entailment, allusion, insinuation, innuendo, adumbration, something rotten in the state of Denmark, snake in the grass, secret, darkness, invisibility, imperceptibility, latent, lurking, secret, occult, implied, dormant, abeyant, unapparent, unknown, unseen, in the background, invisible, indiscoverable, dark, impenetrable, unspied, unsuspected, unsaid, unwritten, unpublished, unbreathed, untalked of, untold &c, unsung, unexposed, unproclaimed, undisclosed, unexpressed, not expressed, tacit, undeveloped, solved, unexplained, untraced, undiscovered, untracked, unexplored, uninvented, indirect, crooked, inferential, by inference, by implication, implicit, constructive, allusive, covert, muffled, steganographic, understood, underhand, underground, delitescent, concealed, by a side wind, sub silentio, in the background, behind the scenes, behind one's back, on the tip of one's tongue, secretly, between the lines, thereby hangs a tale, tacitum vivit sub pectore vulnus, where there's smoke, there's fire.