spiracle

noun

1. a small opening allowing the outer air to come through into a confined space; air hole
2. Geol. a small vent formed on the surface of a thick lava flow
3. Zool. an aperture for breathing, as
   1. any of the small external openings of the tracheal respiratory system in most terrestrial arthropods, ordinarily along the sides of certain thoracic and abdominal segments; stigma
   2. any of various similar openings for the passage of air or respiratory water, as in tadpoles
   3. blowhole (sense )