holding fast; characterized by keeping a firm hold (often fol. by of )

a tenacious grip on my arm; tenacious of old habits.

highly retentive

a tenacious memory.

pertinacious, persistent, stubborn, or obstinate.

adhesive or sticky; viscous or glutinous.

holding together; cohesive; not easily pulled asunder; tough.

noun

bullheadedness , doggedness , hardheadedness , mulishness , obstinateness , pertinaciousness , pertinacity , perverseness , perversity , pigheadedness , tenacity , willfulness