Spoilt vote

In voting, a ballot is considered spoilt, spoiled, void, null, informal, invalid or stray if a law declares or an election authority determines that it is invalid and thus not included in the vote count. This may occur accidentally or deliberately. The total number of spoilt votes in a United States election has been called the residual vote.[1] In Australia, such votes are generally referred to as informal votes, and in Canada they are referred to as rejected votes.

Spoilt ballot paper from the 2016 Kazakh legislative election reading "Бойкот Выборам" which means Boycott the elections.
Spoilt ballot paper from the 2021 UK Police and Crime Commissioner Elections

    In some jurisdictions spoilt votes are counted and reported.