“BIOLOGICAL IMMORTALITY refers to a stable or decreasing rate of mortality from senescence, thus decoupling it from chronological age. Various unicellular and multicellular species, including some vertebrates, achieve this state either throughout their existence or after living long enough. A biologically immortal living being can still die from means other than senescence, such as through injury or disease. The term is also used by biologists to describe cells that are not subject to the Hayflick limit.”
https://en.m.wikipedia.org/wiki/Biological_immortality