tenacious in WordNet English dictionary

1. sticking together
   "two coherent sheets"; "tenacious burrs"
   coherent  tenacious 
   
2. stubbornly unyielding
   "dogged persistence"; "dour determination"; "the most vocal and pertinacious of all the critics"; "a mind not gifted to discover truth but tenacious to hold it"- T.S.Eliot; "men tenacious of opinion"
   dogged  dour  persistent  pertinacious  tenacious  unyielding 
   
3. good at remembering
   "a retentive mind"; "tenacious memory"
   retentive  recollective  long  tenacious