What is 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 called?

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. (Webster's 1913.)

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