Spartan, Spartanic, adamant, adamantine, astringent, austere, authoritarian, beetle-browed, black-browed, black, bleak, cast-iron, cheerless, cold, crabbed, dark, dejected, demanding, dismal, dreary, dumpish, exacting, exigent, firm, flinty, forbidding, frowning, fundamentalist, gloomy, glowering, glum, grim, grum, hard-core, hard-nosed, hard, hardy, harsh, hidebound, immovable, immutable, implacable, impliable, inclement, inelastic, inexorable, inflexible, intransigent, iron, ironbound, ironclad, ironhanded, irreconcilable, lowering, melancholy, meticulous, moodish, moody, mopey, moping, mopish, morose, mumpish, muscle-bound, obdurate, obstinate, orthodox, procrustean, purist, puristic, puritan, puritanic, relentless, rigid, rigorist, rigoristic, rigorous, rock-ribbed, rockbound, rough, rugged, saturnine, scowling, severe, sour, steely, stern, stiff, straightlaced, straitlaced, strict, stringent, stubborn, sulky, sullen, surly, tough, ugly, unaffected, unalterable, unbending, unchangeable, uncompromising, unfriendly, ungentle, ungiving, unmoved, unrelenting, unsparing, unyielding