The Collaborative International Dictionary of English v.0.48:

Egotism \E"go*tism\ (?; 277), n. [L. ego I + ending -tism for
   -ism, prob. influenced by other English words in -tism fr.
   the Greek, where t is not part of the ending, as baptism. See
   Egoism.]
   The practice of too frequently using the word I; hence, a
   speaking or writing overmuch of one's self; self-exaltation;
   self-praise; the act or practice of magnifying one's self or
   parading one's own doings. The word is also used in the sense
   of egoism.
   [1913 Webster]

         His excessive egotism, which filled all objects with
         himself.                                 --Hazlitt.

   Syn: Egotism, Self-conceit, Vanity, Egoism.
        Self-conceit is an overweening opinion of one's talents,
        capacity, attractions, etc.; egotism is the acting out
        of self-conceit, or self-importance, in words and
        exterior conduct; vanity is inflation of mind arising
        from the idea of being thought highly of by others. It
        shows itself by its eagerness to catch the notice of
        others. Egoism is a state in which the feelings are
        concentrated on one's self. Its expression is egotism.
        [1913 Webster]

WordNet (r) 3.0 (2006):

egotism
    n 1: an exaggerated opinion of your own importance [syn:
         egotism, self-importance, swelled head]
    2: an inflated feeling of pride in your superiority to others
       [syn: ego, egotism, self-importance]