balloon fish

from The Collaborative International Dictionary of English v.0.48

balloonfish \bal*loon"fish`\, balloon fish \bal*loon" fish`\
   (Zool.)
   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}.
   [1913 Webster + WordNet 1.5]

from The Collaborative International Dictionary of English v.0.48

Bur fish \Bur" fish`\ (Zool.)
   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}.
   [1913 Webster]

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