“knife” – English explanatory dictionary

noun an instrument used for cutting, with a sharp metal blade fixed in a handle ○ Put out a knife, fork and spoon for each person. ○ You need a sharp knife to cut meat. □ on a knife edge in a difficult position, where you are not sure what will happen ■ verb to stab someone with a knife ○ He was knifed in the back during the fight. (NOTE: knifes – knifing – knifed)

“to KNIFE a person,” to stab; an un-English custom, but a very
common expression.

n.; pl. Knives (#). [OE. knif, AS. cnif; akin to D. knijf, Icel. knifr, Sw. knif, Dan. kniv.]
1. 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..
2. A sword or dagger. “The coward conquest of a wretch’s knife.” Shak. Knife grass (Bot.) a tropical American sedge (Scleria latifolia), having leaves with a very sharp and hard edge, like a knife. — War to the knife, mortal combat; a conflict carried to the last extremity.

v. t. [imp. & p. p. Knifed p. pr. & vb. n. Knifing ]
1. (Hort.) To prune with the knife.
2. To cut or stab with a knife. [Low]

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). [Slang, U. S.]