expression, i-adjective
having little time left to live; one's days are numbered
Used to describe someone who is terminally ill or very old and not expected to live much longer. Often carries a solemn or literary tone.
医者から余命いくばくもないと宣告された。
The doctor told him he had little time left to live.
余命いくばくもない祖父は、家族に囲まれて穏やかに過ごしている。
My grandfather, whose days are numbered, is spending his remaining time peacefully surrounded by family.
余命 means 'remaining life' or 'life expectancy' as a noun, while 余命いくばくもない is a set phrase meaning 'having little time left to live'.
命短し is a classical expression meaning 'life is short', often used in poetry or proverbs, whereas 余命いくばくもない specifically refers to a person's limited remaining time.
Composed of 余命 (remaining life) + いくばく (how much, how many) + も (even) + ない (not). The phrase literally means 'there is not even much remaining life', i.e., one has very little time left to live.