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]