on one's last legs meaning

• On the verge of utter failure or exhaustion
• 
  [American slang]
  adj. phr. Failing; near the end. The blacksmith's business is on its last legs. The dog is old and sick. He is on his last legs.
  Compare: ONE FOOT IN THE GRAVE, ON ONE'S KNEES².
  

• on one's (or its) last legs:    [American slang]mo ...
• on someone's or something's last legs last:    [American idiom][f ...
• on so's or sth's last legs:    [American slang]Fi ...