Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
pertinacious is an adjective meaning "stubbornly unyielding". It carries one recorded sense.
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”
“men tenacious of opinion”
Definitions, synonyms and semantic relations for pertinacious come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.