The Collaborative International Dictionary of English v.0.48:

Frigatoon \Frig"a*toon`\, n. [It. fregatone: cf. F.fr['e]gaton.
   See Frigate.] (Naut.)
   A Venetian vessel, with a square stern, having only a
   mainmast, jigger mast, and bowsprit; also a sloop of war
   ship-rigged.
   [1913 Webster]