Source : Webster's Revised Unabridged Dictionary (1913)

Atheist \A"the*ist\, n. [Gr. ? without god; 'a priv. + ? god:
   cf. F. ath['e]iste.]
   1. One who disbelieves or denies the existence of a God, or
      supreme intelligent Being.

   2. A godless person. [Obs.]

   Syn: Infidel; unbeliever.

   Note: See {Infidel}.

Source : WordNet®

atheist
     adj : related to or characterized by or given to atheism; "atheist
           leanings" [syn: {atheistic}, {atheistical}]

atheist
     n : someone who denies the existence of god