water level (Noun) — The level of the surface of a body of water.
water level (Noun) — Underground surface below which the ground is wholly saturated with water. ex. "spring rains had raised the water level"
water level (Noun) — A line corresponding to the surface of the water when the vessel is afloat on an even keel; often painted on the hull of a ship.
water level (Noun) — A water gauge that shows the level by showing the surface of the water in a trough or U-shaped tube.