1. (in biology) The state or process of aging, especially in humans; old age.
2. (in cell biology) Ceasing to divide by mitosis because of shortening of telomeres or excessive DNA damage.
3. (in gerontology) Old age; accumulated damage to macromolecules, cells, tissues and organs with the passage of time.
4. (in botany) Fruit senescence, leading to ripening of fruit.
Origin: 1650-60 From Latin: senescere: to grow old.
adjective: senescent: growing old, aging.