Source : Webster's Revised Unabridged Dictionary (1913)

Anthem \An"them\, n. [OE. antym, antefne, AS. antefen, fr. LL.
   antiphona, fr. Gr. ?, neut. pl. of ? antiphon, or anthem, n.
   neut., from ? sounding contrary, returning a sound; ? over
   against + ? sound, voice: the anthem being sung by the
   choristers alternately, one half-choir answering the other:
   cf. OF. anthaine, anteine, antieune, F. antienne. See
   {Antiphon}.]
   1. Formerly, a hymn sung in alternate parts, in present
      usage, a selection from the Psalms, or other parts of the
      Scriptures or the liturgy, set to sacred music.

   2. A song or hymn of praise. --Milton.

Anthem \An"them\, v. t.
   To celebrate with anthems. [Poet.]

         Sweet birds antheming the morn.          --Keats.
   ||

Source : WordNet®

anthem
     n 1: a song of devotion or loyalty (as to a nation or school)
     2: a song of praise (to God or to a saint or to a nation) [syn:
         {hymn}]