The Collaborative International Dictionary of English v.0.48:

Meatus \Me*a"tus\, n. sing. & pl.; E. pl. Meatuses. [L., a
   going, passage, fr. meare to go.] (Anat.)
   A natural passage or canal; as, the external auditory meatus.
   See Illust. of Ear.
   [1913 Webster]