Wordnet 3.0
ADJECTIVE (1)
1. 
 not representative of a group, class, or type; 
- Example: "a group that is atypical of the target audience"- Example: "a class of atypical mosses"- Example: "atypical behavior is not the accepted type of response that we expect from children"[syn: atypical, untypical]
WordNet (r) 3.0 (2006):
untypical
    adj 1: not representative of a group, class, or type; "a group
           that is atypical of the target audience"; "a class of
           atypical mosses"; "atypical behavior is not the accepted
           type of response that we expect from children" [syn:
           atypical, untypical] [ant: typical]