† thaˈlassiarchObs.rare—0. [f.Gr. θαλάσσι-ος marine, maritime + -αρχος ruling, ruler.] Hence † thaˈlassiarchyObs.rare—0. (See quots.) 1656Blount Glossogr., Thalassiarck, an Admiral or chief Officer at sea.1727Bailey vol. II, Thalassiarchy, the Admiralship, or the office of the Admiral.