Source : Webster's Revised Unabridged Dictionary (1913)

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}.

Source : WordNet®

meatus
     n : a natural body passageway