senescent

adjective3

1. •
   Growing old; decaying with the lapse of time.

   • And now, as the night was senescent / ⁠And star-dials pointed to morn— / ⁠As the star-dials hinted of morn— / At the end of our path a liquescent / ⁠And nebulous lustre was born — 1859
2. •
   That ceases to divide.

   • When such lines and forms of organic development prevail, the individual, as the cell of the body, becomes soon senescent, drifting inevitably into age, decay, and death. — 1919
3. •
   Characteristic of old age.