Source : Webster's Revised Unabridged Dictionary (1913)

Philosopher \Phi*los"o*pher\, n. [OE. philosophre, F.
   philosophe, L. philosophus, Gr. ?; ? loving + ? wise. Cf.
   {Philosophy}.]
   1. One who philosophizes; one versed in, or devoted to,
      philosophy.

            Then certain philosophers of the Epicureans, and of
            the Stoics, encountered him.          --Acts xvii.
                                                  18.

   2. One who reduces the principles of philosophy to practice
      in the conduct of life; one who lives according to the
      rules of practical wisdom; one who meets or regards all
      vicissitudes with calmness.

   3. An alchemist. [Obs.] --Chaucer.

   {Philosopher's stone}, an imaginary stone which the
      alchemists formerly sought as instrument of converting the
      baser metals into gold.

Source : WordNet®

philosopher
     n 1: a specialist in philosophy
     2: a wise person who is calm and rational; someone who lives a
        life of reason with equanimity