n. (Mach.) (a) A weight which is dropped into a bore, as of an oil well, to explode a cartridge previously lowered. (b) A device, as a loosely fitted plug, which is driven through a pipe by the pressure of the contents behind the plug to clear away obstructions. (c) A rough sled or dray used for dragging logs, hauling stone, etc. [ Local, U. S. ] [ Webster 1913 Suppl. ]