1.Definition: good at remembering

"Tenacious memory"

Related Adjective(s):long, recollective, retentive

2.Definition: sticking together

"Tenacious burrs"

Related Adjective(s):coherent

3.Definition: stubbornly unyielding

"A mind not gifted to discover truth but tenacious to hold it", "Men tenacious of opinion"

Related Adjective(s):dogged, dour, persistent, pertinacious, unyielding