assiduous, balking, balky, bigoted, bulldogged, bulldoggish, bulletheaded, bullheaded, case-hardened, clamant, clamorous, constant, continuing, crying, demanding, diligent, dogged, dogmatic, draining, enduring, exacting, exigent, exorbitant, extortionate, faithful, fanatic, fixed, game, gamy, grasping, gritty, gutsy, gutty, hardheaded, headstrong, immutable, importunate, inalterable, indefatigable, indomitable, industrious, insistent, instant, intolerant, invincible, lasting, loud, loyal, mettlesome, mulish, nervy, never-tiring, obstinate, opinionated, overzealous, patient, patient as Job, permanent, perseverant, persevering, persistent, persisting, perverse, pigheaded, plodding, plucky, plugging, preoccupied, pressing, rapt, red-blooded, refractory, relentless, resolute, restive, sedulous, self-willed, set, single-minded, sleepless, slogging, spirited, spiritful, spunky, stable, steadfast, steady, stiff-necked, strong-willed, strongheaded, stubborn, sulky, sullen, taxing, tenacious, tireless, tough, unabating, unconquerable, uncooperative, undaunted, undiscouraged, undrooping, unfailing, unfaltering, unflagging, unflinching, unintermitting, uninterrupted, unnodding, unregenerate, unrelaxing, unrelenting, unremitting, unshakable, unsleeping, unswerving, untiring, unwavering, unwearied, unwearying, unwinking, unyielding, urgent, utterly attentive, weariless, willful