Source : Webster's Revised Unabridged Dictionary (1913)

Atonement \A*tone"ment\, n.

   {Day of Atonement} (Jewish Antiq.), the only fast day of the
      Mosaic ritual, celebrated on the tenth day of the seventh
      month (Tisri), according to the rites described in
      Leviticus xvi. Atrium \A"tri*um\, n. (Anat.)
   A cavity, entrance, or passage; as, the atrium, or atrial
   cavity, in the body wall of the amphioxus; an atrium of the
   infundibula of the lungs, etc.

Source : WordNet®

Day of Atonement
     n : (Judaism) a solemn Jewish fast day; 10th of Tishri; its
         observance is one of the requirements of the Mosaic Law
         [syn: {Yom Kippur}]