Source : Webster's Revised Unabridged Dictionary (1913)

Mass \Mass\, n. [OE. masse, messe, AS. m[ae]sse. LL. missa, from
   L. mittere, missum, to send, dismiss: cf. F. messe. In the
   ancient churches, the public services at which the
   catechumens were permitted to be present were called missa
   catechumenorum, ending with the reading of the Gospel. Then
   they were dismissed with these words : ``Ite, missa est''
   [sc. ecclesia], the congregation is dismissed. After that the
   sacrifice proper began. At its close the same words were said
   to those who remained. So the word gave the name of Mass to
   the sacrifice in the Catholic Church. See {Missile}, and cf.
   {Christmas}, {Lammas}, {Mess} a dish, {Missal}.]
   1. (R. C. Ch.) The sacrifice in the sacrament of the
      Eucharist, or the consecration and oblation of the host.

   2. (Mus.) The portions of the Mass usually set to music,
      considered as a musical composition; -- namely, the Kyrie,
      the Gloria, the Credo, the Sanctus, and the Agnus Dei,
      besides sometimes an Offertory and the Benedictus.

   {Canon of the Mass}. See {Canon}.

   {High Mass}, Mass with incense, music, the assistance of a
      deacon, subdeacon, etc.

   {Low Mass}, Mass which is said by the priest through-out,
      without music.

   {Mass bell}, the sanctus bell. See {Sanctus}.

   {Mass book}, the missal or Roman Catholic service book.