dissenting vote; vote against
A vote cast in opposition to a proposal, motion, or candidate; often used in formal or organizational settings.
The dissenting votes were in the majority on that proposal.
He cast a vote against the plan.
賛成投票 means a vote in favor, the opposite of 反対投票.
棄権 means abstention from voting, whereas 反対投票 is an active vote against.
Compound of 反対 (opposition) and 投票 (vote).