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blow·hole

(blōhōl′)

1. An opening or one of a pair of openings for breathing, located on the top of the head of cetaceans, such as whales and dolphins. The blowhole is opened by muscles upon surfacing and closed by the pressure of water upon diving.

2. A hole in ice to which aquatic mammals, such as dolphins, come to breathe.

3. A vent to permit the escape of air or other gas.

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blowhole

bottlenose dolphin

Indo-European & Semitic Roots Appendices

Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

Indo-European Roots

Semitic Roots

The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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