WordWeb Online

1. Good at remembering
   "tenacious memory";
   - retentive, recollective, long
    
2. Stubbornly persisting, refusing to give up
   "a mind not gifted to discover truth but tenacious to hold it"; "men tenacious of opinion";
   - dogged, dour, persistent, pertinacious, unyielding
    
3. Sticking together
   "tenacious burrs";
   - coherent

See also: adhesive, aware, mindful, obstinate, stubborn, unregenerate

Encyclopedia: Tenacious