penetrable

impregnable, penetrable, impermeable, inscrutable, impervious, indecipherable, unclimbable, indestructible, invisible, opaque, porous, unscalable, incomprehensible, undecipherable, omnipresent, unbreakable, cloaked, unmovable, thick, airtight, unfathomable, invulnerable, unconquerable, unstoppable, assailable, bulletproof, undistinguishable, dense, otherworldly, untouchable, immovable, conquerable, inhospitable, fortified, watertight, impossible, suffocating, implacable, invincible, crenelated, unnavigable, stygian, arcane, swiss cheese, labyrinthine, inaccessible, infallible, baffling, unflappable, obscure, multilayered, ironclad, shrouded, unyielding, adamantine, labyrinthian, unbendable, unreadable, fearsome, devoid, maddening, unrecognizable, unforgiving, featureless, maginot line, unsearchable, insurmountable, barren, ringed, immutable, honeycombed, brittle, nonexistent, depthless, chinked, unreachable, nondescript, impassable, uncontainable, flimsy, useless, uninviting, jungly, iron curtain, indistinguishable, imperturbable, formless, unremarkable, unanswerable, abstruse, flawless, befuddled, fissured, intricate, nebulous, unshakable, unperceived, obtuse, graspable, enigmatic, insuperable, immoveable, betrayals, deals, delinquencies, favors, favour, favours, heartache, indictments, miscarriages, mischief, murderers, pos, sins, transgressions, annoyance, anyone, be, beforehand, bitterness, thickest, densest, obscuring, denser, sombre, inky, tangled, thickening, trackless, vaporous, blacker, dun, gloomy, shadowy, thorny

crataegus monogyna, english hawthorn, iron curtain, jungle, mangrove, myrtle oak, quercus myrtifolia, rhizophora mangle, seaside scrub oak, smother

dense, heavy, incomprehensible, thick, uncomprehensible