say it: an-tuh-THET-i-kuhl
antithetical 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 antithetical come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.