rigid

rigid adjective austere, dour, durus, exact, exacting, firm, firmly set, fixed, flinty, formal, hard, harsh, hidebound, indurate, indurated, indurative, inelastic, inexorable, intractable, motionless, obdurate, obstinate, orthodox, precise, punctilious, puritanical, relentless, renitent, rigidus, rigorous, set, severe, severus, starched, starchy, static, steely, stern, stiff, stony, straitlaced, strict, stringent, stubborn, taut, tense, tough, unadaptable, unalterable, uncompromising, unconformable, undeviating, unmalleable, unmitigated, unmoving, unpliant, unrelaxed, unrelenting, unyielding, wooden

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See also: close, compact, draconian, exact, factual, firm, fixed, formal, inflexible, ironclad, irreconcilable, literal, meticulous, narrow, orthodox, particular, pertinacious, precise, provincial, punctilious, relentless, renitent, severe, solid, static, strict, stringent, unalterable, unbending, uncompromising, unmitigated, unrelenting, unyielding