Source : Webster's Revised Unabridged Dictionary (1913)

Mutualism \Mu"tu*al*ism\, n. (Ethics)
   The doctrine of mutual dependence as the condition of
   individual and social welfare. --F. Harrison. --H. Spencer.
   --Mallock.

Source : WordNet®

mutualism
     n : the relation between two different species of organisms that
         are interdependent; each gains benefits from the other
         [syn: {symbiosis}]