The Collaborative International Dictionary of English v.0.48:

Halleluiah \Hal`le*lu"iah\, Hallelujah \Hal`le*lu"jah\
   (h[a^]l`l[-e]*l[=u]"y[.a]), n. & interj. [Heb. See
   Alleluia.]
   Praise ye Jehovah; praise ye the Lord; -- an exclamation used
   chiefly in songs of praise or thanksgiving to God, and as an
   expression of gratitude or adoration. --Rev. xix. 1 (Rev.
   Ver. )
   [1913 Webster]

         So sung they, and the empyrean rung
         With Hallelujahs.                        --Milton.
   [1913 Webster]

         In those days, as St. Jerome tells us,"any one as he
         walked in the fields, might hear the plowman at his
         hallelujahs."                            --Sharp.
   [1913 Webster]

WordNet (r) 3.0 (2006):

hallelujah
    n 1: a shout or song of praise to God

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "hallelujah":
   Agnus Dei, Benedicite, Gloria, Gloria Patri, Gloria in Excelsis,
   Introit, Magnificat, Miserere, Nunc Dimittis, Te Deum, Trisagion,
   Vedic hymn, alleluia, answer, anthem, antiphon, antiphony,
   applause, canticle, chant, cheer, chorale, chorus of cheers, cry,
   doxology, hooray, hosanna, hurrah, hurray, huzzah, hymn,
   hymn of praise, hymnody, hymnography, hymnology, laud, mantra,
   motet, offertory, offertory sentence, paean, psalm, psalmody, rah,
   report, response, responsory, shout, versicle, yell, yippee



Easton's 1897 Bible Dictionary:

Hallelujah
   praise ye Jehovah, frequently rendered "Praise ye the LORD,"
   stands at the beginning of ten of the psalms (106, 111-113, 135,
   146-150), hence called "hallelujah psalms." From its frequent
   occurrence it grew into a formula of praise. The Greek form of
   the word (alleluia) is found in Rev. 19:1, 3, 4, 6.


Hitchcock's Bible Names Dictionary (late 1800's):

Hallelujah, praise the Lord