on your last legs

on its/(one's) last legs

1. slang Of a machine, near a complete breakdown or loss of functionality. In this usage, "its" is used between "on" and "last." Judging by all that noise coming from her car, I'm pretty sure it's on its last legs. The blender stopped working again today—it must be on its last legs.
2. slang Of a person, near physical collapse or death. In this usage, a pronoun for the person being discussed is used between "on" and "last." 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

on your last legs

1. If you are on your last legs, you are exhausted. Jackson collapsed as he left the boxing ring, clearly on his last legs.
2. If someone is on their last legs, they are about to die. There was an enormous variety of patients — people who looked in perfect health and people who looked as if they were on their last legs.
See also: last, leg, on

on your last legs

near the end of life, usefulness, or strength.
1987 Eric Newby Round Ireland in Low Gear It is certainly difficult to imagine how anyone who is in any way infirm, and some of the pilgrims who make the climb are literally on their last legs, can reach the top.
See also: last, leg, on

on your/its ˌlast ˈlegs

about to die or stop functioning very soon; be very weak or in bad condition: This photocopier is on its last legs.
See also: last, leg, on