Source : Webster's Revised Unabridged Dictionary (1913)

Psalm \Psalm\, v. t.
   To extol in psalms; to sing; as, psalming his praises.
   --Sylvester.

Psalm \Psalm\, n. [OE. psalm, salm, AS. sealm, L. psalmus,
   psalma, fr. Gr. ?, ?, fr. ? to pull, twitch, to play upon a
   stringed instrument, to sing to the harp: cf. OF. psalme,
   salme, F. psaume.]
   1. A sacred song; a poetical composition for use in the
      praise or worship of God.

            Humus devout and holy psalms Singing everlastingly.
                                                  --Milton.

   2. Especially, one of the hymns by David and others,
      collected into one book of the Old Testament, or a modern
      metrical version of such a hymn for public worship.

Source : WordNet®

Psalm
     n 1: one of the 150 lyrical poems and prayers that comprise the
          Book of Psalms in the Old Testament; said to have been
          written by David
     2: any sacred song used to praise the Deity