Inside diameter of a pipe or tube.

1. The diameter of a piston-cylinder mechanism as found in reciprocating engines, pumps, and compressors.

2. To penetrate or pierce with a rotary tool.

3. To machine a workpiece to increase the size of an existing hole in it.

1. A tunnel under construction.

2. To cut or drill a hole for blasting, water infusion, exploration, or water or firedamp drainage.

1. A high, breaking wave of water, advancing rapidly up an estuary. Also known as eager; mascaret; tidal bore.

2. A submarine sand ridge, in very shallow water, whose crest may rise to intertidal level.

The interior of a gun barrel or tube.