The Oxford Thesaurus An A-Z Dictionary of Synonyms - tenacious adj.

1) persistent, dogged, unfaltering, pertinacious, unswerving, determined, diligent, resolute, staunch, stalwart, steadfast, strong, sturdy, unwavering, strong-willed, strong-minded, unshaken, unshakeable or unshakable, obstinate, intransigent, stubborn, adamant, obdurate, refractory, immovable, inflexible, rigid, firm, unyielding, uncompromising: Despite his age, Christopher maintains a tenacious grip on reality. 2) cohesive, strong, tough; adhesive, sticky, clinging; gummy, gluey, mucilaginous, glutinous, viscous, viscid: The bricks are then smeared over with a tenacious mud, which dries hard. 3) Often, tenacious of. clinging (to) , grasping, maintaining, keeping (up) , staying with, retentive (of) , persisting or persistent (in) , retaining: She is tenacious of the old ways of doing things. 4) retentive, good: Aunt Agatha has a very tenacious memory.