indigestion, any or all of the symptoms—abdominal discomfort, belching, flatulence, aversion to eating, nausea, vomiting, diarrhea, constipation, heartburn—associated with the malfunctioning of the digestive system. Indigestion may be caused by disease, but it primarily occurs because of stress, improper eating habits, excessive smoking, exorbitant consumption of coffee or alcohol, or hypersensitivity to particular foods. Indigestion can be alleviated by avoiding the foods or drinks that seem to cause it and by not smoking.