The Collaborative International Dictionary of English v.0.48:

Specimen \Spec"i*men\, n. [L., fr. specere to look, to behold.
   See Spy.]
   A part, or small portion, of anything, or one of a number of
   things, intended to exhibit the kind and quality of the
   whole, or of what is not exhibited; a sample; as, a specimen
   of a man's handwriting; a specimen of a person's blood; a
   specimen of painting; aspecimen of one's art.
   [1913 Webster +PJC]

   Syn: Sample; model; pattern.

   Usage: Specimen, Sample. A specimen is a representative
          of the class of things to which it belongs; as, a
          specimen of photography. A sample is a part of the
          thing itself, designed to show the quality of the
          whole; as, a sample of sugar or of broadcloth. A
          cabinet of minerals consists of specimens; if a part
          be broken off from any one of these, it is a sample of
          the mineral to which it belongs. "Several persons have
          exhibited specimens of this art before multitudes of
          beholders." --Addison. "I design this but for a sample
          of what I hope more fully to discuss." --Woodward.
          [1913 Webster]

WordNet (r) 3.0 (2006):

specimen
    n 1: an example regarded as typical of its class
    2: a bit of tissue or blood or urine that is taken for
       diagnostic purposes; "they collected a urine specimen for
       urinalysis"

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "specimen":
   case, case history, case in point, cross section, embodiment,
   example, exemplar, exponent, illustration, instance, little bite,
   little smack, model, pattern, piece, representation,
   representative, sample, sampling, sort, species, swatch, taste,
   taster, type, typification, variety



Bouvier's Law Dictionary, Revised 6th Ed (1856):

SPECIMEN. A sample; a part of something by which the other may be known.
     2. The act of congress of July 4, 1836, section 6, requires the
inventor or discoverer of an invention or discovery to accompany his
petition and specification for a patent with specimens of ingredients, an of
the composition of matter, sufficient in quantity for the purpose of
experiment, where the invention or discovery is of the composition of
matter.