- hang by a thread
- hang by a hair & hang by a thread1. 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.
* * *or[hang by a hair] {v. phr.} To depend on a very small thing; be in doubt. * /For three days Tom was so sick that his life hung by a thread./ * /As Joe got ready to kick a field goal, the result of the game hung by a hair./ Compare: HANG IN THE BALANCE.
Dictionary of American idioms. 2013.