rocklike, intransigent, heartless, adamantine, flinty, firm, refractory, wayward, impenitent, resist, die-hard, fixed, heady, immovable, iron, attitude, hard-boiled, intractable, unremorseful, cussed, unregenerate, unrelenting, granitic, compassionless, hardened, rocky, inexorable, unfeeling, incompliant, perverse, bouldered, flint, brassbound, unrepentant, remorseless, stonyhearted, implacable, unflinching, uncompliant, opinionated, granitelike, contumacious, unconquerable, hardhearted, unregenerated, cold-hearted, cold-blooded, study at inflexible, decided, resolved, callous, bouldery
obstinate (part of speech: adjective)
tenacious (part of speech: adjective)
hard, brave, indefatigable, diligent, dogged, tireless, steadfast, plucky, tough, bold, unflagging, bullheaded, devoted, strong-willed, dauntless, true, decisive, indomitable, stony, bulldogged, insistent, courageous, staunch, enduring, undaunted, flintlike, headstrong, faithful, strong, fervent, spunky, determined, persevering, stiff, persistent, hearty
severe (part of speech: adjective)
demanding, rigid, austere, fundamental, gruff, rigorous, brusque, dry, uncompromising, precise, curt, piquant, correct, brisk, chilly, obstinate, icy, stiff-necked, bleak, meticulous, disciplined, cutting, spare, stringent, hidebound, blunt, caustic, censorious, keen, cool, tart, exacting, basic, acute, sharp, ascetic, acerbic, imperial, raw, astringent, prudish, lean, severe, frosty, Spartan, Draconian, harsh, acrimonious, unbending, intense, puritanical, oppressive, intolerant, critical, authoritarian, short, abrupt, strict, stern, relentless, stark, inflexible, crisp, grim, strait-laced, dour
- One of them was telling the other that her sister's husband, a mason, had died an obdurate heathen and a bitter enemy of the Christian Church. - "The Complete Historical Romances of Georg Ebers", Georg Ebers.
- He has proved himself a hard man to me, cruel and obdurate beyond all my fears; but I know he is not altogether heartless. - "Charlotte's Inheritance", M. E. Braddon.
- She 's not obdurate. - "The Complete Project Gutenberg Works of George Meredith", George Meredith.