un·​der·​sea | \ˌən-dər-ˈsē \

Definition of undersea 

(Entry 1 of 2)

1 : being or carried on under the sea or under the surface of the sea undersea oil deposits undersea fighting

2 : designed for use under the surface of the sea an undersea fleet


\ˌən-dər-ˈsēz \
variants: or underseas

Definition of undersea (Entry 2 of 2)

: under the sea : beneath the surface of the sea photographs taken undersea

Examples of undersea in a Sentence


They are conducting undersea research.

Recent Examples on the Web: Adjective

The island is connected to New York’s power grid through undersea cables that officials disabled this week. Adam Janofsky, WSJ, "Federal Researchers Simulate Power Grid Cyberattack, Find Holes in Response Plan," 9 Nov. 2018 The new class will be considerably larger and more capable than the current Virginia class, with an emphasis on undersea combat. Kyle Mizokami, Popular Mechanics, "The Navy’s Next Attack Submarine Will Be Big, Expensive," 22 Oct. 2018 The new technology also involves adjustments to the electronic circuitry to allow the torpedo to better operate in its undersea environment. Kris Osborn, Fox News, "Navy pursues new stealthy heavyweight attack torpedo," 10 Sep. 2018 The South China Sea has heavily traveled shipping lanes, rich fishing grounds and potential oil, gas and other undersea mineral deposits. David S. Cloud, latimes.com, "Pentagon bars China from joining naval exercise in the Pacific," 23 May 2018 The city also has plans to add undersea attractions for those walking off the beach: a near-shore recreational underwater trail just east of the city’s main parking lot. Anne Geggis, Sun-Sentinel.com, "A rainforest of the sea: Deerfield looks to net more tourists with underwater attractions," 8 July 2018 Buoyed by a military shift in strategy that relies more on undersea warfare, Electric Boat is on track to build two submarines a year, with a third in design. Stephen Singer, courant.com, "Malloy Promises Nearly $85M For Electric Boat Job Creation," 1 May 2018 For example: In 2012, Curran notes, Japanese auto sales in China took a dive after the countries squared off over control of the East China Sea and undersea mineral rights. Joseph N. Distefano, Philly.com, "New Trump import fees: How will China fight back?," 11 July 2018 Nicole Duennebier’s paintings imagine undersea life in the manner of 17th-century Dutch still lifes, heaving with ravishing abundance. Cate Mcquaid, BostonGlobe.com, "‘Pushing Painting’ presents the medium’s possibilities," 20 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'undersea.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of undersea


1613, in the meaning defined at sense 1


1645, in the meaning defined above

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Statistics for undersea

Last Updated

16 Nov 2018

Look-up Popularity

Time Traveler for undersea

The first known use of undersea was in 1613

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English Language Learners Definition of undersea

: found, done, or used below the surface of the sea


un·​der·​sea | \ˈən-dər-ˈsē \

Kids Definition of undersea

1 : being or done under the sea or under the surface of the sea an undersea volcano

2 : used under the surface of the sea an undersea vessel

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