Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
antithetic is an adjective meaning "sharply contrasted in character or purpose". It carries one recorded sense.
sharply contrasted in character or purpose
“practices entirely antithetical to her professed beliefs”
“hope is antithetic to despair”
Definitions, synonyms and semantic relations for antithetic come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.