senile

senile
    adj 1: mentally or physically infirm with age; "his mother was
           doddering and frail" [syn: {doddering}, {doddery},
           {gaga}, {senile}]
    

Senile \Se"nile\, a. [L. senilis, from senex, gen. senis, old,
   an old man: cf. F. s['e]nile. See {Senior}.]
   Of or pertaining to old age; proceeding from, or
   characteristic of, old age; affected with the infirmities of
   old age; as, senile weakness. "Senile maturity of judgment."
   --Boyle.
   [1913 Webster]

   {Senile gangrene} (Med.), a form of gangrene occuring
      particularly in old people, and caused usually by
      insufficient blood supply due to degeneration of the walls
      of the smaller arteries.
      [1913 Webster]
    

56 Moby Thesaurus words for "senile":
      aged, aging, ancient, anile, childish, childlike, crabbed,
      debilitated, declining, decrepit, doddered, doddering, doddery,
      doited, dotard, doting, dotty, enfeebled, failing, feeble, fogy,
      fogyish, forgetful, fossilized, fuddy-duddy, gerontal, gerontic,
      infirm, mossbacked, moth-eaten, mummylike, old, old fart, old fogy,
      old-fogy, old-fogyish, palsied, papery-skinned, ravaged with age,
      rickety, run to seed, rusty, senescent, shaky, shattered,
      shriveled, simple, stodgy, stricken in years, stuffy, timeworn,
      tottering, tottery, weak, withered, wizened