Antithetical

 WORD OF THE DAY

antithetical / adjective / an-tuh-THET-ih-kul

Definition
1a: being in direct and unequivocal opposition
1b: directly opposite or opposed
2: constituting or marked by antithesis

Examples
"In all seriousness, area trails can get crowded, particularly during holidays, and an adventure with too many others, for some, is antithetical to their preferred outdoor experience."
 — David Jasper, The Bulletin (Bend, Oregon), 26 Nov. 2021

Prime Minister Narendra Modi is self-consciously an agent of historical change, as much as Nehru, but often in an antithetical mode.
— Raghu Karnad, The New Yorker, 26 Oct. 2021

Did You Know?
Antithetical and antithesis come from Greek antitithenai ("to oppose").
The oldest sense of antithesis refers to a language pattern that contrasts parallel ideas, as in "action, not words" or "they promised freedom and provided slavery," and antithetical originally referred to anything that was marked by such antithesis.
For example, you could say "The phrase 'action, not words' is an antithetical construction."
It is more common, however, for antithesis to mean "the exact opposite" and for antithetical to mean "directly opposite."