What exactly is a ghost gun? The term "ghost gun" is used by media, police, and sometimes the firearms industry to describe homemade weapons devoid of serial numbers or other identifying markings that enable them to be tracked to their maker, seller, or original owner. For years, law enforcement authorities referred to these weapons as simply "homemade" guns or "kit" guns. "Ghost gun" is a relatively new term. How are ghost guns made? A variety of ways. The most... (GunPolicy.org)