To discredit someone means to damage their reputation or make people stop believing or trusting them. When you discredit a person's ideas, you show why those ideas are wrong or unreliable. When you discredit the person themselves, you harm how others see their character or honesty.

Imagine a student who always shares helpful study tips. If someone proves those tips are actually incorrect and harmful, they've discredited the advice. If they go further and spread rumors that the student cheats, they're trying to discredit the student personally.

Scientists work hard to discredit false theories by gathering evidence that proves them wrong. A lawyer might try to discredit a witness by showing they contradict themselves or have a reason to lie. Sometimes people try to discredit others unfairly, attacking someone's reputation instead of actually addressing their arguments, which is a dishonest debate tactic.

The word can also be used as a noun for something that brings shame: a student who plagiarizes their essay becomes a discredit to their school. When your actions make people lose respect for you or what you represent, you discredit yourself.