Ventilation. Also: an opening which allows the passage of air, heat, steam, etc.; a vent. Obsolete.

A vent, esp. for a conduit.

a hole or vent for breathing or ventilation; spec. a hole in the ice where a seal or other aquatic mammal surfaces to breathe.

= suspiral, n. 2.

A hole or passage to admit air; esp. a hole in a layer of ice formed over deep water, providing a breathing-place for aquatic animals or divers.

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

A comparatively small opening for the passage of air, etc.; an air-hole or vent-hole.

An air-hole or vent-hole.

†(a) the opening at the top of the windpipe, the glottis; (b) an opening in brickwork for the passage of air; (c) the hole in the lower board of a…

= spiracle, n.1 2.

A hole through which air or gas escapes (see quots.); spec. for the escape of foul air from underground passages, of steam from railway tunnels…