adj. 25B6; adjective DETERMINED, purposeful, resolved, adamant, single-minded, firm, unswerving, unwavering, steadfast, staunch, stalwart, unfaltering, unhesitating, persistent, indefatigable, tenacious, strong-willed, unshakeable; stubborn, dogged, obstinate, obdurate, inflexible, intransigent, implacable, unyielding, unrelenting; spirited, brave, bold, courageous, plucky, indomitable; N. Amer. rock-ribbed; informal gutsy, spunky; formal pertinacious.
half-hearted.