The definition of antithetical is something that is contrary or opposite.(adjective)
An example of something that is antithetical is eating meat if you are a vegetarian.
See antithetical in Webster's New World College Dictionary
Origin: obs. antithetic, opposite (< Gr antithetikos < antithenai: see antithesis) + -al
See antithetical in American Heritage Dictionary 4
Origin: From Medieval Latin antitheticus
Origin: , from Greek antithetikos
Origin: , from antitithenai, to oppose; see antithesis.
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