n, pl  knives   1  :  any of various instruments used in surgery primarily to sever tissues: as  a  :  a cutting instrument consisting of a sharp blade attached to a handle  b  :  an instrument that cuts by means of an electrical current  2  :  SURGERY 3 - usu. used in the phrase under the knife <went under the this morning>  <was afraid of the >  .
 
 
 
Similar sounding terms:  na·ive  NF 
 
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