Meaning of Mare Undarum

Ma're Un•da'rum

Pronunciation: (un-där'um), [key]
  1. (Sea of Waves) a dark plain in the first quadrant of the face of the moon: about 4800 sq. mi. (12,000 sq. km).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.