on last legs

Related to on last legs: on its last legs

on (one's) last legs

Near physical collapse or death. I knew I was on my last legs, so I was very relieved to see the marathon's finish line in the distance. Ed's on his last legs—you should probably try to visit him in the hospital today.
See also: last, leg, on
Farlex Dictionary of Idioms.

on someone's (or something's) last legs

Fig. for someone or something to be almost worn out or finished. This building is on its last legs. It should be torn down. I feel as if I'm on my last legs. I'm really tired.
See also: last, leg, on
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

on (one's) last legs

At the end of one's strength or resources; ready to collapse, fail, or die.
See also: last, leg, on
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • on (one's) last legs
  • on one’s last legs
  • on one's last legs
  • on your last legs
  • Let’s have it!
  • let's have it
  • the last of the lot
  • last but not least
  • win the wooden spoon
  • in the last chance saloon