tenacious

1 ENTRIES FOUND:
tenacious /təˈneɪʃəs/ adjective
tenacious
/təˈneɪʃəs/
adjective
Britannica Dictionary definition of TENACIOUS
[more tenacious; most tenacious]
1 
a  : not easily stopped or pulled apart : firm or strong
b  : continuing for a long time
2 
: very determined to do something

— tenaciously

adverb

— tenacity

/təˈnæsəti/ noun [noncount]