N. 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

V. render hard, harden, stiffen, indurate, petrify, temper, ossify, vitrify, accrust

Adj. 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 a board