An example of something that is antithetical is eating meat if you are a vegetarian.
A viewpoint that was antithetical to conventional wisdom.
His wrong-headed beliefs are antithetical to everything we stand for as a community.
This is precisely why insistence on relative truth is antithetical to critical thinking.
Origin of antithetical
- From Medieval Latin antitheticus from Greek antithetikos from antitithenai to oppose antithesis
From American Heritage Dictionary of the English Language, 5th Edition