To remonstrate means to protest or argue against something you think is wrong or unwise, often with someone in authority. When you remonstrate with someone, you're making a serious, reasoned argument about why they should change their mind or their actions.

Picture a student who notices their teacher made a grading mistake. Instead of just accepting it, the student remonstrates with the teacher, calmly explaining why the answer should count as correct. Or imagine a group of citizens who remonstrate with their town council about a decision to cut funding for the library, presenting careful arguments about why it matters to the community.

The word carries a sense of earnestness and respect, even while disagreeing. You remonstrate when you care enough about something to speak up thoughtfully, presenting reasoned arguments rather than angry outbursts. A coach might remonstrate with a referee over a bad call, or a daughter might remonstrate with her parents about an unfair curfew.

The word suggests you're trying to persuade someone by appealing to their sense of reason or fairness. You're essentially saying, “Please reconsider this, because here's why it's a problem.”