1. A small passage made with a needle through stemming, for admitting a squib to enable the charge to be lighted.

2. A hole, extending up through the bearing at the top of the core-barrel inner tube, which allows the water and air in the upper part of the inner tube to escape into the borehole.

3. A small hole in the upper end of a core-barrel inner tube that allows water and air in the inner tube to escape into the annular space between the inner and outer barrels.

4. An opening provided for the discharge of pressure or the release of pressure from tanks, vessels, reactors, processing equipment, and so on.

5. A pipe for providing airflow to or from a drainage system or for circulating air within the system to protect trap seals from siphonage and back pressure.

The opening of a volcano on the surface of the earth.

A small opening in a casting mold to allow for the escape of gases.

The external opening of the cloaca or rectum, especially in fish, birds, and amphibians.