Source : Webster's Revised Unabridged Dictionary (1913)

Balloon fish \Bal*loon" fish`\ (Zo["o]l.)
   A fish of the genus {Diodon} or the genus {Tetraodon}, having
   the power of distending its body by taking air or water into
   its dilatable esophagus. See {Globefish}, and {Bur fish}.