adamant, adamantine, assiduous, cast-iron, constant, continuing, de longue haleine, diligent, dogged, dour, endless, enduring, extended, faithful, filled out, firm, flinty, fundamentalist, grim, hard-core, hard, hidebound, immovable, immutable, implacable, impliable, inalterable, indefatigable, indomitable, industrious, inelastic, inexorable, inflexible, insistent, intransigent, invincible, iron, ironbound, ironclad, ironhanded, irreconcilable, lasting, lengthy, long-drawn-out, long-spun, long-winded, long, longiloquent, loyal, merciless, mortal, muscle-bound, never-tiring, obdurate, obstinate, orthodox, padded, patient, patient as Job, permanent, perseverant, persevering, persistent, persisting, pertinacious, plodding, plugging, preoccupied, procrustean, prolix, protracted, purist, puristic, puritan, puritanic, rapt, relentless, resolute, rigid, rigorist, rigoristic, rigorous, rock-ribbed, rockbound, ruthless, sedulous, single-minded, sleepless, slogging, spun-out, stable, steadfast, steady, steely, stern, stiff, straightlaced, straitlaced, stubborn, talkative, tenacious, tireless, unabating, unaffected, unalterable, unappeasable, unbending, unchangeable, uncompromising, unconquerable, undaunted, undiscouraged, undrooping, unfailing, unfaltering, unflagging, unflinching, ungiving, unintermitting, uninterrupted, unmoved, unnodding, unrelaxing, unremitting, unsleeping, unswerving, untiring, unwavering, unwearied, unwearying, unwinking, unyielding, utterly attentive, verbose, weariless, windy, wordy