What is "balloon fish"

balloonfish \bal*loon"fish`\, balloon fish \bal*loon" fish`\ (Zo["o]l.) A fish of the genus Diodon (such as Diodon holocanthus) or the genus Tetraodon, having the power of distending its body by taking air or water into its dilatable esophagus. It is similar to but smaller than the porcupinefish. See Globefish, and Bur fish.

Bur fish \Bur" fish`\ (Zo["o]l.) A spinose, plectognath fish of the Allantic coast of the United States (esp. Chilo mycterus geometricus) having the power of distending its body with water or air, so as to resemble a chestnut bur; -- called also ball fish, balloon fish, and swellfish.