Source : Webster's Revised Unabridged Dictionary (1913)

Memorial Day \Me*mo"ri*al Day\
   A day, May 30, appointed for commemorating, by decorating
   their graves with flowers, by patriotic exercises, etc., the
   dead soldiers and sailors who served the Civil War (1861-65)
   in the United States; Decoration Day. It is a legal holiday
   in most of the States. In the Southern States, the
   Confederate Memorial Day is: May 30 in Virginia; April 26 in
   Alabama, Florida, Georgia, and Mississippi; May 10 in North
   Carolina and South Carolina; the second Friday in May in
   Tennessee; June 3 in Louisiana. [U. S.]

Memorial \Me*mo"ri*al\, a. [F. m['e]morial, L. memorialis, fr.
   memoria. See {Memory}.]
   1. Serving to preserve remembrance; commemorative; as, a
      memorial building.

            There high in air, memorial of my name, Fix the
            smooth oar, and bid me live to fame.  --Pope.

   2. Contained in memory; as, a memorial possession.

   3. Mnemonic; assisting the memory.

            This succession of Aspirate, Soft, and Hard, may be
            expressed by the memorial word ASH.   --Skeat.

   {Memorial Day}. Same as {Decoration Day}. [U.S.]

Source : WordNet®

Memorial Day
     n : U.S., last Monday in May; commemorates the members of the
         United States armed forces who were killed in war [syn: {Decoration
         Day}]