The Collaborative International Dictionary of English v.0.48:

Unauthorized \Unauthorized\
   See authorized.

WordNet (r) 3.0 (2006):

unauthorized
    adj 1: not endowed with authority [syn: unauthorized,
           unauthorised] [ant: authorised, authorized]
    2: without official authorization; "an unauthorized strike";
       "wildcat work stoppage" [syn: unauthorized, unauthorised,
       wildcat]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "unauthorized":
   actionable, against the law, anarchic, anarchistic, anomic, banned,
   barred, black-market, bootleg, chargeable, contraband,
   contrary to law, criminal, felonious, flawed, forbade, forbid,
   forbidden, illegal, illegitimate, illicit, impermissible,
   irregular, justiciable, lawless, nonconstitutional, nonlegal,
   nonlicit, nonpermissible, not permitted, off limits, out of bounds,
   outlaw, outlawed, prohibited, punishable, ruled out, taboo,
   tabooed, triable, unallowed, unapproved, unconstitutional,
   under the ban, under-the-counter, under-the-table, unlawful,
   unlicensed, unofficial, unpermissible, unsanctioned, unstatutory,
   untouchable, unwarrantable, unwarranted, verboten, vetoed,
   wrongful