galleass \gal"leass\ ?; 135, n. f. gal'easse, gal'eace;
   cf. it. galeazza, sp. galeaza; ll. galea a galley. see
   galley. naut.
   a large galley, having some features of the galleon, as
   broadside guns; esp., such a vessel used by the southern
   nations of europe in the 16th and 17th centuries. see
   galleon, and galley. written variously galeas,
   gallias, etc.
   1913 webster

   note: "the galleasses . . . were a third larger than the
         ordinary galley, and rowed each by three hundred galley
         slaves. they consisted of an enormous towering
         structure at the stern, a castellated structure almost
         equally massive in front, with seats for the rowers
         amidships." --motley. gallegan
see also:
galley galleon galeas gallias