Philistinism, armor, callosity, callousness, callus, flintiness, formidable defenses, hard heart, hard shell, hardenedness, hardheartedness, hardness, hardness of heart, heart of stone, imperviousness, insensitiveness, insensitivity, inuredness, obduracy, obdurateness, rhinoceros hide, stoniness, thick skin
impenitence, irrepentance, recusance, lack of contrition, hardness of heart, seared conscience, induration
, obduracy, impenitent, uncontrite, obdurate, hard, hardened, seared, recusant, unrepentant, relentless, remorseless, graceless, shriftless, lost, incorrigible, irreclaimable, unreconstructed, unregenerate, unreformed, unrepented, unreclaimed, unatoned.
hardness, rigidity, renitence, renitency, inflexibility, temper, callosity, durity, induration
, petrifaction, lapidification, lapidescence, vitrification, ossification, crystallization, stone, pebble, flint, marble, rock, fossil, crag, crystal, quartz, granite, adamant, bone, cartilage, hardware, heart of oak, block, board, deal board, iron, steel, cast iron, decarbonized iron, wrought iron, nail, brick, concrete, cement, hard, rigid, stubborn, stiff, firm, starch, starched, stark, unbending, unlimber, unyielding, inflexible, tense, indurate, indurated, gritty, proof, adamant, adamantine, adamantean, concrete, stony, granitic, calculous, lithic, vitreous, horny, corneous, bony, osseous, ossific, cartilaginous, hard as a rock, stiff as buckram, stiff as a poker, stiff as starch, stiff as as board.