senescent

from WordNet (r) 3.0 (2006)

senescent
    adj 1: growing old [syn: {aging}, {ageing}, {senescent}]

from The Collaborative International Dictionary of English v.0.48

Senescent \Se*nes"cent\, a. [L. senescent, p. pr. of senescere
   to grow old, incho. fr. senere to be old.]
   Growing old; decaying with the lapse of time. "The night was
   senescent." --Poe. "With too senescent air." --Lowell.
   [1913 Webster]