Definitions of knife:

• noun:   edge tool used as a cutting instrument; has a pointed blade with a sharp edge and a handle
• noun:   a weapon with a handle and blade with a sharp point
• noun:   any long thin projection that is transient
• verb:   use a knife on

  Example: "The victim was knifed to death"

• name:  A surname (very rare: popularity rank in the U.S.: #62795)