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]

WordNet (r) 3.0 (2006):

Scabiosa atropurpurea
    n 1: Old World annual having fragrant purple to deep crimson
         flower heads; naturalized in United States [syn: sweet
         scabious, pincushion flower, mournful widow, Scabiosa
         atropurpurea]