hang by a thread/hair

hang by a thread

1. Literally, to be attached only by single thread, strand, or something similar. If that button is only hanging by a thread, you're bound to lose it during the course of the day.
2. To be perilously close to failing, dying, or resulting in a bad outcome. After the loss, their chances of getting into the championships are hanging by a thread. Her life hung by a thread as medics rushed her to the hospital.
See also: by, hang, thread
Farlex Dictionary of Idioms.

hang by a hair

 and hang by a thread 
1. Lit. to hang by something very thin, such as a thread or a hair. The tiniest part of the mobile hung by a thread, the rest are on plastic cords.
2. and hang on by a hair; hang on by a thread Fig. to depend on something very insubstantial; to hang in the balance. Your whole argument is hanging by a thread. John isn't failing geometry, but his passing grade is just hanging by a hair.
See also: by, hair, hang
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

hang by a thread

Also, hang by a hair. Be in a risky or unstable situation, as in His promotion was hanging by a thread, or With the lead actor sick, the success of our play hung by a hair. This expression, already proverbial in the early 1500s, alludes to Damocles, who vexed King Dionysius with constant flattery. The king invited him to a banquet where Damocles found himself seated under a naked sword suspended by a single hair, symbolizing his insecure position at the court.
See also: by, hang, thread
The American Heritage® Dictionary of Idioms by Christine Ammer.

hang by a thread

1. If something hangs by a thread, it is very likely to fail, although it has not failed yet. It's clear that the ceasefire is hanging by a thread. England's World Cup hopes hang by a thread and they must now rely on the results of the others in their group going their way.
2. If someone's life hangs by a thread, they are seriously ill and are very likely to die. His kidneys had failed and his life was hanging by a thread. Note: This expression may relate to the story of the Sword of Damocles: see the explanation at `sword'.
See also: by, hang, thread
Collins COBUILD Idioms Dictionary, 3rd ed.

hang by a thread

be in a highly precarious state.
See also: by, hang, thread
Farlex Partner Idioms Dictionary

hang by a ˈthread/ˈhair

be in a very uncertain situation: After the operation, his life hung by a thread for several hours. The future of this company hangs by a thread. Unless we get two or three big orders by the end of the month, we’re finished.
See also: by, hair, hang, thread
Farlex Partner Idioms Dictionary
See also:
  • hang by a thread
  • hang by a thread, to
  • hang (on) by a hair
  • hang by a hair
  • the eye of a needle
  • eye of the needle
  • thread the needle
  • thread through
  • thread through (something)
  • thread and thrum