The Collaborative International Dictionary of English v.0.48:

Quintessence \Quin*tes"sence\, v. t.
   To distil or extract as a quintessence; to reduce to a
   quintessence. [R.] --Stirling. "Truth quintessenced and
   raised to the highest power." --J. A. Symonds.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quintessence \Quin*tes"sence\, n. [F., fr. L. quinta essentia
   fifth essence. See Quint, and Essence.]
   1. The fifth or last and highest essence or power in a
      natural body. See Ferment oils, under Ferment. [Obs.]
      [1913 Webster]

   Note: The ancient Greeks recognized four elements, fire, air,
         water, and earth. The Pythagoreans added a fifth and
         called it nether, the fifth essence, which they said
         flew upward at creation and out of it the stars were
         made. The alchemists sometimes considered alcohol, or
         the ferment oils, as the fifth essence.
         [1913 Webster]

   2. Hence: An extract from anything, containing its rarest
      virtue, or most subtle and essential constituent in a
      small quantity; pure or concentrated essence.
      [1913 Webster]

            Let there be light, said God; and forthwith light
            Ethereal, first of things, quintessence pure,
            Sprung from the deep.                 --Milton.
      [1913 Webster]

   3. The most characteristic form or most perfect example of
      some type of object.
      [PJC]

WordNet (r) 3.0 (2006):

quintessence
    n 1: the fifth and highest element after air and earth and fire
         and water; was believed to be the substance composing all
         heavenly bodies [syn: quintessence, ether]
    2: the purest and most concentrated essence of something
    3: the most typical example or representative of a type

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "quintessence":
   archetype, axiom, beau ideal, bottom, center, champion, choice,
   chosen, classic, concentrate, concentration, core, cream,
   decoction, distillate, distillation, elect, elite, elixir,
   embodiment, epitome, essence, essential, essentiality, exemplar,
   extract, extraction, fabric, fat, flower, focus, fundamental, gist,
   gravamen, heart, hypostasis, ideal, infusion, inner essence,
   kernel, last word, marrow, masterpiece, masterwork, material,
   matter, meat, medium, mirror, model, nonesuch, nonpareil, nub,
   nucleus, nuts and bolts, optimum, paragon, pattern of perfection,
   personification, pick, pith, postulate, prime, principle, prize,
   prototype, purification, queen, quid, quiddity, quintessential,
   refinement, sap, select, soul, spirit, stuff, substance,
   sum and substance, superlative, the best, the best ever,
   the nitty-gritty, the tops, the very best, ultimate, very model,
   virtuality