NOUN (2)

1. a specialist in philosophy;

2. a wise person who is calm and rational; someone who lives a life of reason with equanimity;

The Collaborative International Dictionary of English v.0.48:

Philosopher \Phi*los"o*pher\, n. [OE. philosophre, F.
   philosophe, L. philosophus, Gr. filo`sofos; fi`los loving +
   sofo`s wise. Cf. Philosophy.]
   1. One who philosophizes; one versed in, or devoted to,
      philosophy.
      [1913 Webster]

            Then certain philosophers of the Epicureans, and of
            the Stoics, encountered him.          --Acts xvii.
                                                  18.
      [1913 Webster]

   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.
      [1913 Webster]

   3. An alchemist. [Obs.] --Chaucer.
      [1913 Webster]

   Philosopher's stone, an imaginary stone which the
      alchemists formerly sought as the instrument of converting
      the baser metals into gold.
      [1913 Webster] Philosophic

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

265 Moby Thesaurus words for "philosopher":
   Abelard, Albertus Magnus, Albinus, Alexander, Anaxagoras, Anselm,
   Averroist, Bacon, Berkeleian, Berkeley, Boethius, Bonaventure,
   Boodin, Bosanquet, Bowne, Broad, Bruno, Cartesian, Chubb, Cicero,
   Comtist, Condillac, Condorcet, Confucius, Cousin, Croce, Cynic,
   Cyrenaic, Drake, Eleatic, Epicurean, Eretrian, Euhemerus, Fechner,
   Feigl, Ferdinand, Fichtean, Frege, Fullerton, Gentile, Gilson,
   Green, Haeckel, Hahn, Haldane, Harris, Hartmann, Hegel, Hegelian,
   Heidegger, Heideggerian, Heraclitean, Heraclitus, Herbart,
   Herbartian, Herder, Hobbes, Holt, Howison, Hume, Humist, Husserl,
   Husserlian, Hutcheson, John, Kantian, Kierkegaard, Kierkegaardian,
   La Mettrie, Langer, Leibniz, Leibnizian, Leucippus, Locke, Lotze,
   Lovejoy, Lucretius, Mach, Marx, Marxist, Mead, Megarian, Mencius,
   Mill, Moore, Moses, Neo-Hegelian, Neo-Pythagorean, Neoplatonist,
   Ockham, Ortega y Gasset, Paley, Parmenidean, Parmenides, Pascal,
   Peripatetic, Perry, Philo, Plato, Platonist, Plotinus, Porphyry,
   Pratt, Pritchard, Protagoras, Pyrrho, Pyrrhonist, Pythagoras,
   Pythagorean, Reid, Reynaud, Roger, Rogers, Ross, Rousseau, Royce,
   Russell, Samuel, Santayana, Sartre, Sartrian, Scheler, Schelling,
   Schiller, Schleiermacher, Schlick, Scholastic, Schopenhauer,
   Scotist, Sellars, Socrates, Socratist, Sophist, Spencerian,
   Spinozist, Stern, Stoic, Strong, Thales, Thomas Aquinas, Thomist,
   Whitehead, Wittgensteinian, academician, agnostic, animist,
   authority, bookman, casuist, classicist, clerk,
   colossus of knowledge, cosmologist, cosmotheist, deist,
   dialectical materialist, dialectician, doctor, dualist, eclectic,
   egoist, elder, elder statesman, empiricist, essentialist,
   existentialist, genius, giant of learning, great soul, guru,
   hedonist, humanist, hylomorphist, hylotheist, hylozoist, idealist,
   illuminate, immaterialist, individualist, intellect, intellectual,
   intuitionist, learned clerk, learned man, literary man,
   litterateur, logical empiricist, logicaster, logician, logistician,
   lover of learning, lover of wisdom, mahatma, man of intellect,
   man of learning, man of letters, man of wisdom, mandarin, master,
   mastermind, materialist, mechanist, mentalist, mentor,
   metaphysician, mine of information, monist, mystic, naturalist,
   nominalist, ontologist, oracle, organic mechanist, organicist,
   panpsychist, pantheist, philologist, philologue, philomath,
   philosophaster, philosophe, philosophizer, physicist, polyhistor,
   polymath, positivist, pragmatist, psychist, pundit, rabbi,
   ratiocinator, rationalist, rationalizer, realist, reasoner, rishi,
   sage, sapient, savant, scholar, scholastic, schoolman,
   secular humanist, seer, sensationalist, sensist, skeptic, sophist,
   speculator, starets, student, substantialist, syllogist,
   syllogizer, syncretist, theist, thinker, transcendentalist,
   utilitarian, vitalist, voluntarist, walking encyclopedia, wise man,
   wise old man, zetetic