: to react to something too strongly : to respond to something with too strong an emotion or with unnecessary or excessive action
I was furious and yelled at him. He told me I was overreacting and to "chillax." Ben Stein
The world isn't coming to an end. You shouldn't overreact to the negative news. Adam Bryant
Some of his animals had become apprehensive and twitchy, overreacting to sound or touch … Mark Caldwell
But the military police overreacted, using tear gas, rubber bullets and excessive force in front of news cameras that spread the images countrywide. Grant Wahl
… the poisonous surfeit of hormones produced by the overreacting immune system. Shannon Brownlee
Sometimes companies in a little bit of trouble are the best investments because the market has overreacted. Orson C. Clay