hang by a hairto be in an uncertain position and depend on something not substantial, be in doubt, depend on a very small thing
[TahlilGaran] Dictionary of Contemporary English ▲
hang by a hairSee: HANG BY A THREAD.
{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.
[TahlilGaran] English Idioms Dictionary ▲