Source : Webster's Revised Unabridged Dictionary (1913)

Mission \Mis"sion\, n. [L. missio, fr. mittere, missum, to send:
   cf. F. mission. See {Missile}.]
   1. The act of sending, or the state of being sent; a being
      sent or delegated by authority, with certain powers for
      transacting business; comission.

            Whose glorious deeds, but in these fields of late,
            Made emulous missions' mongst the gods themselves.
                                                  --Shak.

   2. That with which a messenger or agent is charged; an
      errand; business or duty on which one is sent; a
      commission.

            How to begin, how to accomplish best His end of
            being on earth, and mission high.     --Milton.

   3. Persons sent; any number of persons appointed to perform
      any service; a delegation; an embassy.

            In these ships there should be a mission of three of
            the fellows or brethren of Solomon's house. --Bacon.

   4. An assotiation or organization of missionaries; a station
      or residence of missionaries.

   5. An organization for worship and work, dependent on one or
      more churches.

   6. A course of extraordinary sermons and services at a
      particular place and time for the special purpose of
      quickening the faith and zeal participants, and of
      converting unbelievers. --Addis & Arnold.

   7. Dismission; discharge from service. [Obs.]

   {Mission school}.
      (a) A school connected with a mission and conducted by
          missionaries.
      (b) A school for the religious instruction of children not
          having regular church privileges.

   Syn: Message; errand; commission; deputation.

Mission \Mis"sion\, v. t.
   To send on a mission. [Mostly used in the form of the past
   participle.] --Keats.

Source : WordNet®

mission
     n 1: an organization of missionaries in a foreign land sent to
          carry on religious work [syn: {missionary post}, {missionary
          station}, {foreign mission}]
     2: an operation that is assigned by a higher headquarters; "the
        planes were on a bombing mission" [syn: {military mission}]
     3: a special assignment that is given to a person or group; "a
        confidential mission to London"; "his charge was deliver a
        message" [syn: {charge}, {commission}]
     4: the organized work of a religious missionary [syn: {missionary
        work}]
     5: a group of representatives or delegates [syn: {deputation},
        {commission}, {delegation}, {delegacy}]