The Collaborative International Dictionary of English v.0.48:

Spurious \Spu"ri*ous\ (sp[=u]"r[i^]*[u^]s), a. [L. spurius.]
   1. Not proceeding from the true source, or from the source
      pretended; not genuine; counterfeit; false; adulterate.
      [1913 Webster]

   2. Not legitimate; bastard; as, spurious issue. "Her spurious
      firstborn." --Milton.
      [1913 Webster]

   Spurious primary, or Spurious quill (Zool.), the first,
      or outer, primary quill when rudimentary or much reduced
      in size, as in certain singing birds.

   Spurious wing (Zool.), the bastard wing, or alula.
      [1913 Webster]

   Syn: Counterfeit; false; adulterate; supposititious;
        fictitious; bastard.
        [1913 Webster] -- Spu"ri*ous*ly, adv. --
        Spu"ri*ous*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

spurious
    adj 1: plausible but false; "a specious claim"; "spurious
           inferences" [syn: specious, spurious]
    2: born out of wedlock; "the dominions of both rulers passed
       away to their spurious or doubtful offspring"- E.A.Freeman
       [syn: bastardly, misbegot, misbegotten, spurious]
    3: intended to deceive; "a spurious work of art" [syn:
       inauthentic, unauthentic, spurious]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "spurious":
   affected, apocryphal, artificial, assumed, baseborn, bastard,
   bogus, brummagem, colorable, colored, contrived, counterfeit,
   counterfeited, deceitful, distorted, dressed up, dummy,
   embellished, embroidered, ersatz, factitious, fake, faked, false,
   falsified, fatherless, feigned, fictitious, fictive, forged,
   fraudulent, garbled, hypocritical, illegitimate, imitation,
   inauthentic, junky, make-believe, man-made, meretricious,
   misbegotten, miscited, miscreated, misquoted, misreported,
   misstated, mock, natural, perverted, phony, pinchbeck, pretend,
   pretended, pseudo, put-on, quasi, queer, self-styled, sham, shoddy,
   simulated, snide, so-called, soi-disant, substitute,
   supposititious, synthetic, tin, tinsel, titivated, twisted,
   unauthentic, unauthoritative, unfounded, ungenuine, unnatural,
   unreal, unreliable, warped