The term 'open ocean' refers to the vast expanse of water that lies beyond the continental shelf and is not affected by land masses. The MAIN crossword solutions for this term are MAIN (4 letters), OUTSEA (6 letters), HIGHSEAS (8 letters), and BOUNDINGMAIN (12 letters). MAIN is a noun meaning the principal part or most important element of something. OUTSEA is an adverb meaning away from the coast or shore. HIGHSEAS is a noun meaning the open ocean, especially the part of it far from land. BOUNDINGMAIN is a noun meaning the open ocean, especially the part of it close to land.