tenacious
Synonyms: adamant, bound, cohesive, determined, fast, firm, forceful, inflexible, intransigent, iron, mulish, obdurate, obstinate, perservering, persistent, persisting, pertinacious, purposeful, relentless, resolute, retentive, set, solid, spunky, stalwart, steadfast, strong-willed, stubborn, sure, tight, tough, true, unforgetful, unshakable, unswerving, unyielding Source: Roget's New Millennium Thesaurus Sign in to see full entry.