(1):

(v. t.) Fig.: To stab in the back; to try to defeat by underhand means, esp. in politics; to vote or work secretly against (a candidate of one's own party).

(2):

(n.) An instrument consisting of a thin blade, usually of steel and having a sharp edge for cutting, fastened to a handle, but of many different forms and names for different uses; as, table knife, drawing knife, putty knife, pallet knife, pocketknife, penknife, chopping knife, etc..

(3):

(v. t.) To prune with the knife.

(4):

(v. t.) To cut or stab with a knife.

(5):

(n.) A sword or dagger.