Cyclic vomiting syndrome: A syndrome characterized by episodes, bouts, or cycles of severe nausea and vomiting that last for hours or even days and alternate with longer asymptomatic periods (with no symptoms). The cause of the syndrome is unknown but it is believed by many experts to be related to migraine.
Cyclic vomiting syndrome (CVS) affects children more often than adults. It starts most commonly between ages 3 and 7. In adults, episodes tend to occur less often but last longer than in children and the events that trigger episodes in adults cannot be pinpointed as easily as they can in children.