We don't have synonyms for galliass yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are gallia, galleass and gallias.
(n) :
(nautical) Alternative spelling of galleass. [(nautical, historical) A type of rowable vessel of the 16th and 17th centuries, similar to a galley but larger, and normally equipped with sails.]
(n) :
(nautical) Alternative spelling of galleass. [(nautical, historical) A type of rowable vessel of the 16th and 17th centuries, similar to a galley but larger, and normally equipped with sails.]