Food is overdone when it has been cooked too much. A steak that is overdone is past the point you wanted: dry, grey, and hard to chew. Vegetables that are overdone are soft and tired. This is everyday kitchen English. You say the meat is overdone, or the cabbage is overdone. Overdone is an adjective here; the verb is overdo. Though actually, people also stretch overdone when something else has been pushed too far — a speech, a joke, the makeup — but that is the same idea, 'too much,' moved out of the kitchen. In cooking talk, overdone is not a compliment, and it is not the same as asking for meat well-done on purpose.