1. geology vent in lava flow: a small vent in a lava flow that allows the escape of built-up gases
2. insects small aperture in insect: a small paired aperture along the side of the thorax or abdomen of an insect or spider through which air enters and leaves
3. fish small gill slit: a small gill slit or opening behind the eye area of some fishes such as skates and rays
4. marine biology blowhole: a blowhole of a whale, dolphin, or similar ocean mammal
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[Early 17th century. Via French< Latin spiraculum< spirare "breathe"]
