The Collaborative International Dictionary of English v.0.48:

Euphemism \Eu"phe*mism\ ([=u]"f[-e]*m[i^]z'm), n. [Gr. ? fr. ?
   to use word of a good omen; e'y^ well + ? to speak: cf. F.
   euph['e]misme. See Fame.] (Rhet.)
   A figure in which a harsh or indelicate word or expression is
   softened; a way of describing an offensive thing by an
   inoffensive expression; a mild name for something
   disagreeable. Euphemistic

WordNet (r) 3.0 (2006):

euphemism
    n 1: an inoffensive or indirect expression that is substituted
         for one that is considered offensive or too harsh [ant:
         dysphemism]