WordWeb Online

1. Of words so related that one contrasts with the other
   "'rich' and 'hard-up' are contrastive terms"
   - incompatible
    
2. Strikingly different; tending to contrast
   "contrastive colours"
   - contrasting
    
3. Syntactically establishing a relation of contrast between sentences or elements of a sentence
   "disjunctive conjunctions like 'but', 'or', or 'though' serve a contrastive function"

See also: antonymous, contrast, different, disjunctive