Used when someone shows strong emotions that don't match the seriousness of the event. Calm down, you're overreacting; it's just a tiny scratch on your car.
Pro Tip 2/3
Context Matters
The word is often used when giving feedback on someone's behavior in a specific situation. When I saw him overreact to the playful teasing, I knew he was having a bad day.
Pro Tip 3/3
Subjective Perception
Whether an action is an overreaction may depend on personal viewpoints. She thinks I overreacted to the news, but it's really important to me.