Synonyms to impassable

dense, Boeotian, adamantine, asinine, beef-brained, beef-witted, blockheaded, blockish, bony, bovine, bristling, broad-bodied, bulky, bullnecked, cement, cemental, chumpish, cloddish, close, close-knit, close-textured, close-woven, coarse, compact, compacted, compressed, concentrated, concrete, condensed, congested, consolidated, corneous, corpulent, cowish, crammed, crammed full, crass, crawling, crowded, diamondlike, dim, dim-witted, doltish, dull, dullard, dumb, duncical, duncish, durable, dure, enduring, exuberant, fat, fatheaded, firm, flintlike, flinty, flourishing, foolish, full, full-bodied, gluey, granitelike, granitic, gross, hard, hard as nails, hardhearted, heaped, heavy, heavyset, horny, impassive, impenetrable, impermeable, ineducable, iron-hard, ironlike, jam-packed, jammed, jungled, jungly, klutzy, lapideous, lasting, lethargic, lithoid, lithoidal, lumpish, lush, luxuriant, marble, marblelike, massed, massive, nonporous, numskulled, oafish, obdurate, obtuse, opaque, osseous, overgrown, overrun, packed, phlegmatic, piled, populous, rank, resistant, resistive, riotous, rocklike, rocky, rugged, ser