A vent or opening. Obsolete. rare.

A hole or opening in a furnace, etc., for escape of smoke and gases or the admission of fresh air.

An opening or aperture in a building, etc., communicating with the outside air.

A small opening by which a confined space has communication with the outer air; esp. an air-hole or air-shaft.

An air-hole or vent-hole.

a gap or hole which contains air or through which air can pass; spec. an air-filled space breaking the continuity of an electric or magnetic…

In extended use. An air-hole or access hole in a furnace.