1. See storm surge. 2. See surge current. 3. See surge line. 4. In hydrology, a sudden change in discharge resulting from the opening or closing of a gate that controls the flow in a channel, or by the sudden introduction of additional water into the channel. 5. The fore and aft movement of the center of gravity of a ship. See heave, sway, ship motion. 6. Water transported up a beach by breaking waves.