To overreact means to respond to something with more emotion or action than the situation really calls for. When someone overreacts, their response is out of proportion to what actually happened.

If you accidentally bump into your friend in the hallway and they start yelling at you like you'd done it on purpose, they're overreacting. The small accident doesn't warrant such a big, angry response. Or imagine spilling a little water on your homework and immediately bursting into tears and declaring the whole assignment ruined, when really you just need to rewrite one line. That's overreacting.

People often overreact when they're already stressed, tired, or worried about something else. A parent might overreact to a small mess in the kitchen because they've had a difficult day. A teacher might overreact to whispered conversation if the class has been especially noisy all week.

Everyone overreacts sometimes. Recognizing when you've done it can help you handle similar situations better next time, and it can help you respond more fairly to other people, too.