BT San 56a(19) :חורפא דסכינא הוא דקא בזע‏ : it is the point of the knife that pierces
See the entire entry for bzˁ vb. to tear up; penetrate

BT San 56a(19) :חורפא דסכינא‏ : point of the knife
See the entire entry for ḥrop̄, ḥurpā n.m. sharp edge; sharpness