low-water markBrE /ˌləʊ ˈwɔːtə mɑːk/ 🔊NAmE /ˌloʊ ˈwɔːtər mɑːrk/ 🔊, /ˌloʊ ˈwɑːtər mɑːrk/ 🔊 nouna line or mark showing the lowest point that the sea reaches at low tide 低潮线；低潮水位标记 OPP high-water mark