WordWeb Online

1. Not similar
   "a group of very dissimilar people"; "a pump not dissimilar to those once found on every farm"; "their understanding of the world is not so dissimilar from our own"; "took different (or dissimilar) approaches to the problem"
    
2. Not alike or similar
   "as dissimilar as two people could be";
   - unalike

See also: alikeness [rare], likeness, similarity, similitude

Antonym: alike, similar