NOUN (3)

1. a philosopher who believes that universals are real and exist independently of anyone thinking of them;

2. a person who accepts the world as it literally is and deals with it accordingly;

3. a painter who represents the world realistically and not in an idealized or romantic style;

The Collaborative International Dictionary of English v.0.48:

Realist \Re"al*ist\, n. [Cf. F. r['e]aliste.]
   1. (Philos.) One who believes in realism; esp., one who
      maintains that generals, or the terms used to denote the
      genera and species of things, represent real existences,
      and are not mere names, as maintained by the nominalists.
      [1913 Webster]

   2. (Art. & Lit.) An artist or writer who aims at realism in
      his work. See Realism, 2.
      [1913 Webster]

   3. a person who avoids unrealistic or impractical beliefs or
      efforts. Contrasted to idealist or visionary.
      [PJC]

WordNet (r) 3.0 (2006):

realist
    n 1: a philosopher who believes that universals are real and
         exist independently of anyone thinking of them
    2: a person who accepts the world as it literally is and deals
       with it accordingly
    3: a painter who represents the world realistically and not in
       an idealized or romantic style