1. the level that the surface of water reaches on the hull of a floating ship or boat
Usage: nautical
2. a line or mark indicating the level reached by water
3. the edge of a body of water where it meets the shore or land

Examples

• The ship’s waterline was painted with a distinctive red stripe.
• After the flood, debris marked the waterline on the building’s walls.
• The boat sat low in the water, with cargo nearly reaching the waterline.
• We walked along the waterline, collecting shells in the wet sand.
• The marina’s docks were damaged when the storm surge rose above the normal waterline.
• Engineers measured the waterline to determine the vessel’s displacement.
• High tide brought the waterline much closer to our beach chairs.