counterconvention

noun
coun·​ter·​con·​ven·​tion | \ ˌkau̇n-tər-kən-ˈven(t)-shən How to pronounce counterconvention (audio) \
variants: or counter-convention
plural counterconventions or counter-conventions

Definition of counterconvention

: an assembly of persons gathered in response to or in protest against another assembly : a competing or opposing convention Democrats who gathered Thursday for the Clinton campaign's counterconvention, less than a mile from the Republican National Convention site, blasted the event and vowed their convention next week in Philadelphia would have a kinder tone.— Liz Goodwin

First Known Use of counterconvention

1756, in the meaning defined above

Keep scrolling for more