sea level

American  

noun

1. the horizontal plane or level corresponding to the surface of the sea at mean level between high and low tide.

---

sea level British  

noun

1. the level of the surface of the sea with respect to the land, taken to be the mean level between high and low tide, and used as a standard base for measuring heights and depths

---

sea level Scientific  

1. The level of the ocean's surface. Sea level at a particular location changes regularly with the tides and irregularly due to conditions such as wind and currents. Other factors that contribute to such fluctuation include water temperature and salinity, air pressure, seasonal changes, the amount of stream runoff, and the amount of water that is stored as ice or snow.

2. ◆ The reference point used as a standard for determining terrestrial and atmospheric elevation or ocean depths is called the mean sea level and is calculated as the average of hourly tide levels measured by mechanical tide gauges over extended periods of time.

---

Etymology

Origin of sea level

First recorded in 1800–10

Example Sentences

They might have a better chance Sunday at sea level.

From Los Angeles Times • Apr. 24, 2026

Planters started anew in central Florida, in Polk County and its surroundings, what’s known as the Ridge, the highest part of Florida, and the only part that was never below sea level, historically.

From Slate • Apr. 20, 2026

Last year, the global mean sea level was around 11 centimetres higher than when satellite altimetry records began in 1993.

From Barron's • Mar. 23, 2026

Better understanding these processes will help refine models that estimate future sea level rise.

From Science Daily • Mar. 18, 2026

At the one extreme was Henderson Island, an old coral reef raised above sea level and devoid of stone Other than limestone.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Related Words

• water level