"atypical" in the adjective sense
1. atypical, untypical, atypic
not representative of a group, class, or type
"a class of atypical mosses"
"atypical behavior is not the accepted type of response that we expect from children"
2. atypical, irregular
deviating from normal expectations somewhat odd, strange, or abnormal
"these days large families are atypical"
"atypical clinical findings"
"atypical pneumonia"
"highly irregular behavior"
Source: WordNet® (An amazing lexical database of English)
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