To cook for too long or at too high a temperature.(verb)
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Use "overcook" in a sentence
"Turn the meat regularly until it is just done; be careful not to overcook it."
"Cook the Sausages: Grill over a hot fire, turning regularly, and being careful not to overcook."
"Place romaine, cut-side down, onto the hottest part of the grill and cook for ideally no more than 5 to 10 seconds, until a char is achieved be careful not to overcook and wilt the lettuce."