an individual living thing that is the last survivor of its species or subspecies and whose death consequently means the extinction of that species or subspecies: The endling of the once plentiful passenger pigeons was Martha, who died in a zoo in 1914.
a person who is the last living member of a family line and whose death consequently means the end of that lineage: Sadly, Kenneth, childless and himself an only child, is soon to leave this world, alone and an endling.