The Collaborative International Dictionary of English v.0.48:

Survival \Sur*viv"al\, n. [From Survive.]
   1. A living or continuing longer than, or beyond the
      existence of, another person, thing, or event; an
      outliving.
      [1913 Webster]

   2. (Arhaeol. & Ethnol.) Any habit, usage, or belief,
      remaining from ancient times, the origin of which is often
      unknown, or imperfectly known.
      [1913 Webster]

            The close bearing of the doctrine of survival on the
            study of manners and customs.         --Tylor.
      [1913 Webster]

   Survival of the fittest. (Biol.) See Natural selection,
      under Natural.
      [1913 Webster] Survivance

WordNet (r) 3.0 (2006):

survival of the fittest
    n 1: a natural process resulting in the evolution of organisms
         best adapted to the environment [syn: survival, survival
         of the fittest, natural selection, selection]