Electrogastrogram: A test in which the electrical current generated by the muscle of the stomach is sensed and recorded in a manner very similar to that of an electrocardiogram of the heart. Abbreviated EGG. An EGG is performed by taping electrodes to the skin on the upper abdomen over the stomach. Recordings from the muscle are stored and analyzed by a computer. An EGG is performed to diagnose motility disorders of the stomach, conditions that prevent the muscles of the stomach from working normally.