/ təˈneɪʃəs; NAmE / adjective ( formal )
1.
that does not stop holding sth or give up sth easily; determined :
a tenacious grip
She's a tenacious woman. She never gives up.
The party has kept its tenacious hold on power for more than twenty years.
2.
continuing to exist, have influence, etc. for longer than you might expect
SYN persistent :
a tenacious illness
► ten·acious·ly adverb :
Though seriously ill, he still clings tenaciously to life.
► ten·acity / təˈnæsəti; NAmE / noun [ U ]:
They competed with skill and tenacity.
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WORD ORIGIN
early 17th cent.: from Latin tenax , tenac- (from tenere to hold) + -ious .