water line

American  

[waw-ter lahyn] / ˈwɔ tər ˌlaɪn /

Or waterline

noun

1. Nautical. the part of the outside of a ship's hull that is just at the water level.

2. Naval Architecture. any of a series of lines on the hull plans of a vessel representing the level to which the vessel is immersed or the bottom of the keel.

3. the line in which water at its surface borders upon a floating body.

4. water level.

5. Also called watermark.  a line indicating the former level or passage of water.

   A water line all around the cellar served as a reminder of the flood.

6. a pipe, hose, tube, or other line for conveying water.

7. waterline, the slightly wet inner rim of skin between the upper or lower eyelashes and the eye, especially with reference to the use of eyeliner.

   Apply pencil eyeliner to your upper and lower waterlines.

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water line British  

noun

1. a line marked at the level around a vessel's hull to which the vessel will be immersed when afloat

2. a line marking the level reached by a body of water

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Etymology

Origin of water line

First recorded in 1615–25

Example Sentences

Further assessments, however, found severe impacts below the water line to infrastructure “that supports the safe and functional operation of the harbor.”

From Los Angeles Times • Aug. 5, 2025

Utility crews must reroute a main water line and underground electric lines under the road.

From Los Angeles Times • Mar. 2, 2025

If you notice any patches of grass that seem to be growing faster than everything else, that might indicate a leaking buried water line.

From Seattle Times • May 15, 2024

When all the main generators fail, ships rely on a backup generator that is typically situated above the water line in another area of the ship, with its own fuel source.

From New York Times • Mar. 30, 2024

I take a look into the bathtub and realize that the water line has really receded since Saturday.

From "Dry" by Neal Shusterman and Jarrod Shusterman