A vent for the escape of steam or other gas.
A top-facing opening to a cavity in the ground very near an ocean's shore, leading to a marine cave from which wave water or bursts of air are expelled.
The spiracle, on the top of the head, through which cetaceans breathe.
A vertical opening in the top of a computer case that lets hot air (primarily from the CPU heat sink) escape quickly.
An unintended cavity filled with air in a casting product.
To fill or be filled with air in an unintended cavity.
A device that controls the flow of a gas or fluid through a pipe.
One of the pieces or divisions of bivalve or multivalve shells.
One of the pieces into which certain fruits naturally separate when they dehisce.
One of the two similar portions of the shell of a diatom.
A device that admits fuel and air into the cylinder of an internal combustion engine, or one that allows combustion gases to exit.
One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or control the flow in the opposite direction
A vacuum tube.
A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, such as in the barberry.
One of the leaves of a folding-door, or a window-sash.
To control (flow) by means of a valve.