Bore (engine), the diameter of a cylinder in a piston engine. Bore (wind instruments), the interior chamber of a wind instrument. Gauge (bore diameter), the inner diameter of the barrel of a firearm. Nominal bore, a pipe size standard. Water well, known as a bore in Australia.
A bore (mechanics) can either refer to the diameter of the piston, or the inside diameter of the cylinder which is the same thing, since the piston goes inside the cylindar (these are all parts of a motor).
