The Collaborative International Dictionary of English v.0.48:

Archetype \Ar"che*type\ ([aum]r"k[-e]*t[imac]p), n. [L.
   archetypum, Gr. 'arche`typon, fr. 'arche`typos stamped first
   and as model; 'arche = 'archi + ty`pos stamp, figure,
   pattern, ty`ptein to strike: cf. F. arch['e]type. See
   Arch-, pref.]
   1. The original pattern or model of a work; or the model from
      which a thing is made or formed.
      [1913 Webster]

            The House of Commons, the archetype of all the
            representative assemblies which now meet.
                                                  --Macaulay.
      [1913 Webster]

            Types and shadows of that glorious archetype that
            was to come into the world.           --South.
      [1913 Webster]

   2. (Coinage) The standard weight or coin by which others are
      adjusted.
      [1913 Webster]

   3. (Biol.) The plan or fundamental structure on which a
      natural group of animals or plants or their systems of
      organs are assumed to have been constructed; as, the
      vertebrate archetype.
      [1913 Webster]

WordNet (r) 3.0 (2006):

archetype
    n 1: something that serves as a model or a basis for making
         copies; "this painting is a copy of the original" [syn:
         original, archetype, pilot]

Moby Thesaurus II by Grady Ward, 1.0:

125 Moby Thesaurus words for "archetype":
   Geistesgeschichte, Hegelian idea, Kantian idea, Platonic form,
   Platonic idea, aesthetic form, antetype, antitype,
   archetypal pattern, art form, beau ideal, biotype, blind impulse,
   build, cast, classic, classic example, collective unconscious,
   complex idea, configuration, conformation, criterion, cut, engram,
   epitome, eternal object, eternal universal, example, exemplar,
   fashion, father image, figuration, figure, form, formal cause,
   format, formation, frame, fugleman, fugler, genotype, genre,
   highest category, history of ideas, id, ideal, idealism, ideate,
   ideatum, idee-force, image, imago, imitatee, impression, impulse,
   inborn proclivity, innate idea, inner form, innovation, instinct,
   layout, lead, libido, make, makeup, masterpiece, masterwork,
   matrix, memory, memory trace, mirror, modality, mode, model, mold,
   natural instinct, natural tendency, new departure, noosphere,
   noumenon, original, paradigm, paragon, pattern,
   pattern of perfection, percept, pilot model, precedent,
   primitive self, prototype, quintessence,
   regulative first principle, representative, rule, set, shape,
   significant form, simple idea, stamp, standard, structure, style,
   subconscious urge, subsistent form, the Absolute,
   the Absolute Idea, the Self-determined, the realized ideal,
   transcendent idea, transcendent nonempirical concept,
   transcendent universal, traumatic trace, turn, type, type species,
   type specimen, unconscious memory, universal, universal concept,
   universal essence, unlearned capacity, unreasoning impulse, urtext,
   very model, vital impulse