Source : Webster's Revised Unabridged Dictionary (1913)

Vagus \Va"gus\, a. [L., wandering.] (Anat.)
   Wandering; -- applied especially to the pneumogastric nerve.
   -- n. The vagus, ore pneumogastric, nerve.

Source : WordNet®

vagus
     n : a mixed nerve that supplies the pharynx and larynx and lungs
         and heart and esophagus and stomach and most of the
         abdominal viscera [syn: {vagus nerve}, {nervus vagus}, {pneumogastric},
          {pneumogastric nerve}, {tenth cranial nerve}, {wandering
         nerve}]
     [also: {vagi} (pl)]