knife-edge /ˈnaɪfˌɛʤ/
刀口,刃形邊緣;鋒利的邊緣;刃形支承
Knife-edge n. Mech. 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.
Knife-edge file. See Illust. of File.
◄ ►
knife-edge
n : a narrow boundary; "he lived on a knife-edge between genius
and insanity"