porthole

A small, usually circular window in a ship’s side.

An opening in a fortified wall; an embrasure.

An aperture in a ship’s side, especially one of the apertures through which the guns are protruded and fired.

The opening to the steam-passages into or from a cylinder, or to the exhaust-passage. See port

In zoology, one of the minute apertures or cinclides in the body-wall of a sea-anemone through which the gastric filaments or acontia are protruded.

An embrasure in a ship’s side. See 3d port.

A circular window set in the hull of a ship.

a window in a ship or airplane

an opening (in a wall or ship or armored vehicle) for firing through