I. adjective 1. directly opposed or contrasted; mutually incompatible • people whose religious beliefs are antithetical to mine.
2. connected with, containing, or using the rhetorical device of antithesis. • when praising the government, Pyrocles invokes the familiar oxymoronic and antithetical mode.
II. derivatives 1. antithetic /antɪˈθɛtɪk / adjective
2. antithetically /ˌantɪˈθɛtɪkli / adverb
– origin late 16th cent. (in sense 2): from Greek antithetikos, from antithetos ‘placed in opposition’, from antitithenai ‘set against’.