From Longman Dictionary of Contemporary Englishknife-edgeˈknife-edge noun [singular]1UNCERTAINa situation in which the result is extremely uncertainon a knife-edge
His future in the job is balanced on a knife-edge.
a knife-edge vote2WORRIEDa situation which makes someone very anxiouson a knife-edge
Living with him, she is constantly on a knife-edge.
the knife-edge of insecurity3SHARPsomething that is narrow or sharp