noun Date: 1818 a sharp wedge of steel or other hard material used as a fulcrum for a lever beam in a precision instrument, a sharp narrow knifelike edge
KNIFE-EDGE
Meaning of KNIFE-EDGE in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012