The Collaborative International Dictionary of English v.0.48:

Mourning \Mourn"ing\, a.
   1. Grieving; sorrowing; lamenting.
      [1913 Webster]

   2. Employed to express sorrow or grief; worn or used as
      appropriate to the condition of one bereaved or sorrowing;
      as, mourning garments; a mourning ring; a mourning pin,
      and the like.
      [1913 Webster]

   Mourning bride (Bot.), a garden flower (Scabiosa
      atropurpurea) with dark purple or crimson flowers in
      flattened heads.

   Mourning dove (Zool.), a wild dove (Zenaidura macroura)
      found throughout the United States; -- so named from its
      plaintive note. Called also Carolina dove. See Illust.
      under Dove.

   Mourning warbler (Zool.), an American ground warbler
      (Geothlypis Philadelphia). The male has the head, neck,
      and chest, deep ash-gray, mixed with black on the throat
      and chest; other lower parts are pure yellow.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dove \Dove\ (d[u^]v), n. [OE. dove, duve, douve, AS. d[=u]fe;
   akin to OS. d[=u]ba, D. duif, OHG. t[=u]ba, G. taube, Icel.
   d[=u]fa, Sw. dufva, Dan. due, Goth. d[=u]b[=o]; perh. from
   the root of E. dive.]
   1. (Zool.) A pigeon of the genus Columba and various
      related genera. The species are numerous.
      [1913 Webster]

   Note: The domestic dove, including the varieties called
         fantails, tumblers, carrier pigeons, etc., was
         derived from the rock pigeon (Columba livia) of
         Europe and Asia; the turtledove of Europe, celebrated
         for its sweet, plaintive note, is Columba turtur or
         Turtur vulgaris; the ringdove, the largest of
         European species, is Columba palumbus; the Carolina
         dove, or Mourning dove, is Zenaidura macroura; the
         sea dove is the little auk (Mergulus alle or Alle
         alle). See Turtledove, Ground dove, and Rock
         pigeon. The dove is a symbol of peace, innocence,
         gentleness, and affection; also, in art and in the
         Scriptures, the typical symbol of the Holy Ghost.
         [1913 Webster]

   2. A word of endearment for one regarded as pure and gentle.
      [1913 Webster]

            O my dove, . . . let me hear thy voice. --Cant. ii.
                                                  14.
      [1913 Webster]

   3. a person advocating peace, compromise or conciliation
      rather than war or conflict. Opposite of hawk.
      [PJC]

   Dove tick (Zool.), a mite (Argas reflexus) which infests
      doves and other birds.

   Soiled dove, a prostitute. [Slang] Dovecot

WordNet (r) 3.0 (2006):

mourning dove
    n 1: wild dove of the United States having a mournful call [syn:
         mourning dove, Zenaidura macroura]