This is a portmanteau or blend of the words 'dunce' and 'nonce'. It means not only is the person a nonce, but they are a fucking idiot too.
by ScrimshawSudoNiM September 13, 2022
Toxic member of the fandom of the KPop girl group TWICE. Play on the fandom name of ONCE and pronounced "Dunce".
by BigBlueagain February 26, 2022