TENACIOUS most nearly means:

TENACIOUS means holding firmly to something; persistent, determined, not yielding easily. Example: 'A tenacious investigator never gives up.' From Latin 'tenax' (holding fast), related to 'tenere' (to hold). Synonyms: persistent, determined, resolute, dogged, steadfast, persevering. Antonyms: weak, yielding, irresolute, half-hearted. Related words: TENACITY (noun — the quality of being tenacious); TENANT (one who holds a lease — same root); TENOR (the holding or general course of something). Note the difference between tenacity and stubbornness: tenacity has a positive connotation (admirable persistence toward a goal); stubbornness has a more negative connotation (refusal to change). ASVAB vocabulary often distinguishes nuances of meaning — DETERMINED (positive), STUBBORN (negative), OBSTINATE (more negative), PERSISTENT (neutral or positive). Choosing the closest meaning sometimes requires considering connotation as well as denotation.