Superannuate, v. t. [imp. & p. p. Superannuated; p. pr. & vb. n. Superannuating.] — Webster enters it under “superannuate”
Etymology: [Pref. super- + L. annus a year.]
1. To impair or disquality on account of age or infirmity. Sir T. Browne.
2. To give a pension to, on account of old age or other infirmity; to cause to retire from service on a pension.
1 other Webster entry under this spelling
Superannuate, v. i.
To last beyond the year; -- said of annual plants. [Obs.] Bacon.
Shades of meaning
Fernald has no entry of its own for superannuated; he lists it under antique.
Where he writes about it:
Antiquated is sometimes used of persons in a sense akin to superannuated. — from antique
The antiquated person is out of style and out of sympathy with the present generation by reason of age; the superannuated person is incapacitated for present activities by reason of age. — from antique