air hole

an opening to admit or discharge air.

a natural opening in the frozen surface of a river or pond.

Origin of air hole

First recorded in 1760–70

This is the air-hole, which allows of gaseous exchanges between the atmosphere inside the box and that outside.

The Glow-Worm and Other Beetles |Jean Henri Fabre
The adit of a military mine, is the aperture by which it is dug and charged: the name is also applied to an air-hole or drift.

The Sailor's Word-Book |William Henry Smyth
One man fell into an air-hole below Forty Mile; another was killed and eaten by his dogs; a third was crushed by a falling tree.

Smoke Bellew |Jack London
"We know an air-hole when we see it—and I can't see any of them around here," replied Paul.

Five Little Starrs in the Canadian Forest |Lillian Elizabeth Roy

I knew it must be the light shining through an air-hole, and swam for it.

The Camp in the Snow |William Murray Graydon

air hole

a hole that allows the passage of air, esp for ventilation

a section of open water in a frozen surface

a less common name for air pocket (def. 1)