Vocabulary What does 外洋 (がいよう, gaiyou) mean? 外洋 (がいよう, gaiyou) means open sea; ocean. Quick factsReadingがいようRomajigaiyouPart of speechnoun 外洋がいようgaiyouopen sea; ocean1noun open sea; oceanKanji in this word外outside洋ocean; the West, Western