Either of a pair of nerves that extend from the brain to the heart, lungs, stomach, and other organs of the body: The vagi consist of mixed nerves that have motor and sensory functions and a wider distribution than any of the other cranial nerves.

As students of neural anatomy, the class attended a lecture about the vagi which involved their normal and abnormal functions.

Vague, diffuse, or fleeting pains in the chest or abdomen: Because Jill complained of a tenderness in the area of her stomach that did't seem to get better, her parents took her to see Dr. Match who diagnosed her as having a condition of dolor vagus which involved the vagus nerve.

1. Either of the longest pair of cranial nerves mainly responsible for parasympathetic control (activities that occur when the body is at rest) over the heart and many other internal organs, including thoracic and abdominal viscera or abdominal cavity below the diaphragm but not including the pelvic tissues: The nervi vagi communicate through thirteen main branches, connecting to four areas in the brain.
2. Etymology: from Latin, vagus, "wandering" + nervus, "nerve".