'Psalm' definitions:

Definition of 'Psalm'

noun

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

noun

Any sacred song used to praise the deity

verb

Sing or celebrate in psalms; "He psalms the works of God"

From: GCIDE

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. [1913 Webster]
Humus devout and holy psalms Singing everlastingly. --Milton. [1913 Webster]
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. [1913 Webster]

From: GCIDE

Psalm \Psalm\, v. t. To extol in psalms; to sing; as, psalming his praises. --Sylvester. [1913 Webster]