Definition of "knife-edge"

knife-edge

noun
plural knife-edges
1. A piece of steel sharpened to an acute edge or angle, and resting on a smooth surface, serving as the axis of motion of a pendulum, scale beam, or other piece required to oscillate with the least possible friction.
2. (figuratively) A precarious balance that could be upset by a very small force in either direction.
  Quotations
  […] meanwhile, Biloxi and Vincennes are both in the process of going down and being abandoned, whilst Miami is right on the knife-edge of being recoverable, with three destroyers clustering around offering pumping and additional damage-control crews to try and keep the light cruiser afloat.
  2021 May 5, Drachinifel, 43:40 from the start, in Battle of Samar - What if TF34 was there?‎, archived from the original on 19 August 2022
  Boris Johnson's future on a knife edge after No 10 party apology [title]
  2022 January 12, “Boris Johnson's future on a knife edge after No 10 party apology”, in The Guardian‎
  Polling stations have opened in a knife-edge election in Finland, with polls suggesting the three leading parties are running neck-and-neck and prime minister Sanna Marin may face an uphill battle to stay in power.
  2023 April 2, Jon Henley, “Finland begins voting in knife-edge election”, in The Guardian‎
3. Used other than figuratively or idiomatically: the edge of a knife.