The Collaborative International Dictionary of English v.0.48:

Red Cross \Red Cross\
   1. The crusaders or the cause they represented.
      [Webster 1913 Suppl.]

   2. A hospital or ambulance service established as a result
      of, though not provided for by, the Geneva convention of
      1864; any of the national societies for alleviating the
      sufferings of the sick and wounded war, also giving aid
      and relief during great calamities; also, a member or
      worker of such a society; -- so called from the badge of
      neutrality; the Geneva cross.

   Note: In islamic countries, a similarly motivated affiliated
         organization is called the Red Crescent. The American
         Red Cross was founded in 1881, largely due to the
         initiative of Clara Barton. The [a
         HREF="http:]/www.redcross.org">American Red Cross
         maintains a web page on the internet, where additional
         information can be found.
         [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

Red Cross
    n 1: an international organization that cares for the sick or
         wounded or homeless in wartime