Meaning of Mare Vaporum

Ma're Va•po'rum

Pronunciation: (vā-pôr'um, -pōr'-), [key]
  1. (Sea of Vapors) a dark plain in the first quadrant and near the center of the face of the moon: about 39,000 sq. mi. (101,000 sq. km).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.