blowhole

ilmareikä, sierainaukko The spiracle, on the top of the head, through which cetaceans breathe.
A vent for the escape of gas.
A top-facing opening to a cavity in the ground very near an ocean's shore, that leads to a marine cave from which wave water and/or bursts of air are expelled.
An unintended cavity filled with air in a casting product.
A vertical opening in the top of computer cases, that let hot air, primarily from the CPU heat sink, escape quickly.