Philistine, Quaker-colored, acier, adamant, adamantine, ashen, ashy, aureate, beefy, bony, bouncing, brass, brassy, brazen, bronze, bronzy, callous, calloused, canescent, case-hardened, cast-iron, cement, cemental, cinereous, cinerous, concrete, constant, copper, coppery, corneous, cupreous, cuprous, dapple-gray, dapple, dappled-gray, dappled, dense, diamondlike, dingy, dismal, doughty, dour, dove-colored, dove-gray, dreary, dull, dure, dusty, ferrous, ferruginous, firm, fixed, flintlike, flinty, forceful, forcible, forcy, full-blooded, full-strength, gilt, glaucescent, glaucous, gold-filled, gold-plated, gold, golden, granitelike, granitic, gray-black, gray-brown, gray-colored, gray-drab, gray-green, gray-spotted, gray-toned, gray-white, gray, grayed, grayish, grey, grim, griseous, grizzle, grizzled, grizzly, gutsy, gutty, hale, hard-core, hard, hard as nails, hardened, hardhearted, hardy, hearty, hefty, horny, husky, immovable, immutable, impervious, implacable, impliable, indurate, indurated, inelastic, inexorable, inflexible, insensitive, intransigent, inured, iron-gray, iron-hard, iron, ironlike, irreconcilable, lapideous, lead-gray, lead, leaden, lithoid, lithoidal, livid, loyal, lusty, marble, marblelike, mercurial, mercurous, mighty, mouse-colored, mouse-gray, mousy, nervy, nickel, nickelic, nickeline, obdurate, obstinate, osseous, pachydermatous, pearl-gray, pearl, pearly, pewter, pewtery, potent, powerful, proof against, puissant, quicksilver, red-blooded, relentless, resistant, resistive, rigid, rigorous, robust, robustious, rock-ribbed, rocklike, rocky, rugged, sad, set, settled, silver-gray, silver-plated, silver, silvered, silvery, slate-colored, slaty, smoke-gray, smoky, sober, solid, somber, sot, stalwart, staunch, steadfast, steady, steel-gray, steel, steeled against, steellike, stern, stiff, stone-colored, stonelike, stony, stout, strapping, strong-willed, strong, strong as brandy, strong as strong, sturdy, taupe, thick-skinned, tin, tinny, tough, true, unaffected, unalterable, unbending, unchangeable, uncompromising, undeflectable, unflappable, ungiving, unmoved, unrelenting, unshaken, unswerving, unyielding, vigorous