Source : Webster's Revised Unabridged Dictionary (1913)

Thanksgiving \Thanks"giv`ing\, n.
   1. The act of rending thanks, or expressing gratitude for
      favors or mercies.

            Every creature of God is good, and nothing to be
            refused, if it be received with thanksgiving. --1
                                                  Tim. iv. 4.

            In the thanksgiving before meat.      --Shak.

            And taught by thee the Church prolongs Her hymns of
            high thanksgiving still.              --Keble.

   2. A public acknowledgment or celebration of divine goodness;
      also, a day set apart for religious services, specially to
      acknowledge the goodness of God, either in any remarkable
      deliverance from calamities or danger, or in the ordinary
      dispensation of his bounties.

   Note: In the United States it is now customary for the
         President by proclamation to appoint annually a day
         (usually the last Thursday in November) of thanksgiving
         and praise to God for the mercies of the past year.
         This is an extension of the custom long prevailing in
         several States in which an annual Thanksgiving day has
         been appointed by proclamation of the governor.

Source : WordNet®

Thanksgiving
     n 1: fourth Thursday in November in the United States; second
          Monday in October in Canada; commemorates a feast held
          in 1621 by the Pilgrims and the Wampanoag [syn: {Thanksgiving
          Day}]
     2: a short prayer of thanks before a meal [syn: {grace}, {blessing}]