That has no type; devoid of typical character; irregular; unlike the type(adjective)
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Use "atypic" in a sentence
"Among the older naturalists, such as Pliny and Aristotle, and even in the older historians, whose scope included natural as well as civil and political history, the atypic and bizarre, and especially the aberrations of form or function of the generative organs, caught the eye most quickly."
"The other patients presented a symptomatic vestibularis schwannoma and an atypic meningeoma."