The Collaborative International Dictionary of English v.0.48:

Egoism \E"go*ism\, n. [F. ['e]go["i]sme, fr. L. -ego I. See I,
   and cf. Egotism.]
   1. (Philos.) The doctrine of certain extreme adherents or
      disciples of Descartes and Johann Gottlieb Fichte, which
      finds all the elements of knowledge in the ego and the
      relations which it implies or provides for.
      [1913 Webster]

   2. Excessive love and thought of self; the habit of regarding
      one's self as the center of every interest; selfishness;
      -- opposed to altruism.
      [1913 Webster]

WordNet (r) 3.0 (2006):

egoism
    n 1: (ethics) the theory that the pursuit of your own welfare in
         the basis of morality
    2: concern for your own interests and welfare [syn: egoism,
       egocentrism, self-interest, self-concern, self-
       centeredness] [ant: altruism, selflessness]