1. 
[syn: antithetic, antithetical]
The Collaborative International Dictionary of English v.0.48:
Antithetic \An`ti*thet"ic\, Antithetical \An`ti*thet"ic*al\, a.
   [Gr. ?.]
   Pertaining to antithesis, or opposition of words and
   sentiments; containing, or of the nature of, antithesis;
   contrasted.
   [1913 Webster]
WordNet (r) 3.0 (2006):
antithetic
    adj 1: sharply contrasted in character or purpose; "practices
           entirely antithetical to her professed beliefs"; "hope is
           antithetic to despair" [syn: antithetic,
           antithetical]