What does "blowhole" mean?

Blowhole: A nostril or spiracle in the top of the head of a whale or other cetacean. Note: There are two spiracles or blowholes in the common whales, but only one in sperm whales, porpoises, etc.

Additional senses

  1. 2.A hole in the ice to which whales, seals, etc., come to breathe.
  2. 3.(Founding) An air hole in a casting.

Sources