ventilator; air vent; air release valve
A device or opening for letting air out or in, such as a vent, valve, or breather. Often used in mechanical, plumbing, or packaging contexts.
Open the air vent on the radiator to bleed the air.
This container has an air vent hole.
Compound of 空気 (くうき, 'air') and 抜き (ぬき, the continuative form of 抜く 'to pull out, remove'), literally 'air removal'.