counterinstance

noun

coun·​ter·​in·​stance ˌkau̇n-tər-ˈin(t)-stən(t)s 

variants or counter-instance

plural counterinstances or counter-instances

: a case that contradicts a rule, theory, etc. : exception sense 2

But in science and philosophy, few things are more prized than a clear counter-instance to a putative law or a prospective definition.

—Toni Vogel Carey

Word History

First Known Use

1847, in the meaning defined above