from
The Collaborative International Dictionary of English v.0.48
Galleass \Gal"le*ass\ (?; 135), n. [F. gal['e]asse, gal['e]ace;
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