An implement used or designed to be used to kill or injure a person. See also gun-control law. concealed weapon. A weapon that is carried by someone but is not visible to the ordinary observer's eye. dangerous weapon. An implement or device that is capable of causing serious bodily harm or death; not to be confused with a deadly weapon. A dangerous weapon maybe deadly; a deadly weapon must be dangerous. deadly weapon. Any firearm or other device (crossbow, longbow, bomb, grenade, and so on), ...