Sea level is generally used to refer to mean sea level (MSL), an average level for the surface of one or more of Earth`s oceans from which heights such as elevations may be measured. MSL is a type of vertical datum{spaced ndash}a standardised geodetic reference point{spaced ndash}that is used, for example, as a chart datum in cartography and mari....
The top of the ocean, where the water meets the atmosphere. It's not necessarily level!
• The level of the surface of the sea; any surface on the same level with the sea.
The ocean surface; the mean level between high and low tides. Sea level is used as a reference point in determining land elevation.
The normal level of high-tide, used as a baseline for measuring height or depth.
position of the air-sea interface, to which all terrestrial elevations and submarine depths are referred. The sea level constantly changes at every ... [29 related articles]
Sea' lev'el The level of the surface of the sea; any surface on the same level with the sea. 
The average surface elevation of the world's oceans.
the imaginary line from which sea depth and land elevation are measured.
[n] - level of the ocean`s surface esp that halfway between mean high and low tide
the average height of the ocean's surface, used as a standard for measuring the elevation of land.
noun level of the ocean`s surface (especially that halfway between mean high and low tide); used as a standard in reckoning land elevation or sea depth
Sea level or mean sea level as it is sometimes known, is the average height of the ocean's surface between high and low tide. Changes in tides and wave conditions over time are averaged out to determine a 'still water level' that can be used to identify a real change in sea level or a change in the height of the land that a tidal gauge is measuring...