Roundworm: A type of parasitic worm that hatches in the intestines and lives there. The eggs of the roundworm usually enter the body through contaminated water or food or on fingers placed in the mouth after the hands have touched a contaminated object. Symptoms of roundworm infections include fatigue, weight loss, irritability, poor appetite, abdominal pain, and diarrhea. Treatment with medication results in a cure in about a week. Without treatment, anemia and malnutrition can develop. An example of a roundworm is Trichuris trichiura, also known as the human whipworm. This worm is found worldwide, but infections are most frequent in areas with tropical weather and poor sanitation practices, and among children. Infection with T. trichiura is not foreign to the US; it occurs in the southern US.