Vent

A small aperture designed to provide an outlet from a confined space or a inlet into it. Air vents (which are also used for heating and are sometimes called "louvres") are usually situated at the top of the dashboard pointing upward toward the windshield), in the center of the dashboard (directing the airflow out into the middle of the passenger compartment), on each side of the dashboard (sending the air back along the sides to the rear of the vehicle), and in the center underneath the dashboard (directing air into the front footwells).
[2] A small triangular window for letting air into the passenger compartment.
[3] To expel through a vent; e.g., when bleeding air (through a vent valve or bleed screw) out of a diesel fuel system alter running out of fuel.