WordWeb Online

1. Ostensibly valid, but not actually valid
   "a spurious argument"
    
2. Plausible but false
   "spurious inferences";
   - specious
    
3. False or fake; not what it appears to be
   "a spurious work of art";
   - inauthentic, unauthentic
    
4. [archaic] Born out of wedlock
   "the dominions of both rulers passed away to their spurious or doubtful offspring";
   - bastardly [archaic], misbegot [archaic], misbegotten [archaic]

See also: counterfeit, false, illegitimate, imitative, invalid

Encyclopedia: Spurious