The Collaborative International Dictionary of English v.0.48:

Extrinsic \Ex*trin"sic\, a. [L. extrinsecus; exter on the
   outside + secus otherwise, beside; akin to E. second: cf. F.
   extrins[`e]que. See Exterior, Second.]
   1. Not contained in or belonging to a body; external;
      outward; unessential; -- opposed to intrinsic.
      [1913 Webster]

            The extrinsic aids of education and of artificial
            culture.                              --I. Taylor.
      [1913 Webster]

   2. (Anat.) Attached partly to an organ or limb and partly to
      some other part; -- said of certain groups of muscles.
      Opposed to intrinsic.
      [1913 Webster]

WordNet (r) 3.0 (2006):

extrinsic
    adj 1: not forming an essential part of a thing or arising or
           originating from the outside; "extrinsic evidence"; "an
           extrinsic feature of the new building"; "that style is
           something extrinsic to the subject"; "looking for
           extrinsic aid" [ant: intrinsic, intrinsical]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "extrinsic":
   acquired, adrift, alien, apparent, barbarian, barbaric, barbarous,
   beside the mark, beside the point, beside the question,
   conventionalized, cortical, epidermic, exomorphic, exotic,
   exterior, external, extraneous, extraorganismal, extraterrestrial,
   foreign, foreign-born, formal, formalist, formalistic, formulary,
   fringe, immaterial, impersonal, impertinent, inadmissible,
   inapplicable, inapposite, inappropriate, incidental, inconsequent,
   intrusive, irrelative, irrelevant, legalistic, nihil ad rem,
   nominal, nonessential, nonsubjective, not at issue, objective,
   off the subject, open, out, out-of-the-way, outer, outermost,
   outland, outlandish, outlying, outmost, outside, outstanding,
   outward, outward-facing, parenthetical, pedantic, peripheral,
   public, roundabout, seeming, strange, stylized, superficial,
   surface, ulterior, unearthly, unessential, unrelated