The Collaborative International Dictionary of English v.0.48:

Superannuate \Su`per*an"nu*ate\, v. t. [imp. & p. p.
   Superannuated; p. pr. & vb. n. Superannuating.] [Pref.
   super- + L. annus a year.]
   1. To impair or disquality on account of age or infirmity.
      --Sir T. Browne.
      [1913 Webster]

   2. To give a pension to, on account of old age or other
      infirmity; to cause to retire from service on a pension.
      [1913 Webster]

WordNet (r) 3.0 (2006):

superannuated
    adj 1: too old to be useful; "He left the house...for the
           support of twelve superannuated wool carders"- Anthony
           Trollope [syn: overage, overaged, superannuated,
           over-the-hill]
    2: old; no longer valid or fashionable; "obsolete words"; "an
       obsolete locomotive"; "outdated equipment"; "superannuated
       laws"; "out-of-date ideas" [syn: outdated, out-of-date,
       superannuated]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "superannuated":
   Gothic, Victorian, abandoned, abjured, antediluvian, antiquated,
   antique, archaic, classical, deserted, discontinued, disused,
   done with, emeritus, fossil, fossilized, grown old, in retirement,
   medieval, mid-Victorian, not worth saving, obsolescent, obsolete,
   of other times, old, old-fashioned, old-world, on pension,
   on the shelf, out, out of use, out-of-date, outdated, outmoded,
   outworn, past use, pensioned, pensioned off, petrified,
   relinquished, renounced, resigned, retired, superannuate,
   superseded, worn-out