un·​der·​sea | \ ˌən-dər-ˈsē How to pronounce undersea (audio) \

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


variants: or underseas \ ˌən-​dər-​ˈsēz How to pronounce undersea (audio) \

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

Adjective They are conducting undersea research.
Recent Examples on the Web: Adjective Geopolitics aside, the United States needs to know just how the USS Connecticut’s accident is likely to stress America’s undersea industrial base. Craig Hooper, Forbes, 3 Nov. 2021 Manufacturing a smartphone, tablet or computer as well as the network that supports them consumes considerable resources — everything from mining rare minerals to laying undersea cables for high-speed internet. Irina Ivanova, CBS News, 22 Apr. 2020 The job encompasses everything from submarines and undersea internet cables to secret space planes and reconnaissance satellites in geosynchronous orbit. Garrett M. Graff, Wired, 26 May 2020 Its broad slopes dip by about one degree from the middle toward the edges, whereas a typical undersea volcano has a decline of five to 10 degrees. William W. Sager, Scientific American, 1 May 2020 They all are found amid the colorful corals and sponges and magnificent undersea formations. Chuck Yarborough, cleveland, 12 Apr. 2020 The ocean is normally a fairly noisy place, with the sounds of happy dolphins, lonely whales and diesel-chugging ships saturating the undersea world. Eric Niiler, Wired, 28 Feb. 2020 Two of the undersea cables that connect South Africa to the global network are again suffering outages, dragging down mobile and landline data speeds nationwide. Brian Browdie, Quartz Africa, 30 Mar. 2020 Space, undersea, going after undersea cables, for example, and also cyber. CBS News, 11 Mar. 2020

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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Time Traveler for undersea

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The first known use of undersea was in 1613

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Dictionary Entries Near undersea

under scrutiny



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Last Updated

16 Nov 2021

Cite this Entry

“Undersea.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/undersea. Accessed 27 Nov. 2021.

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More Definitions for undersea



English Language Learners Definition of undersea

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


un·​der·​sea | \ ˈən-dər-ˈsē How to pronounce undersea (audio) \

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

More from Merriam-Webster on undersea

Thesaurus: All synonyms and antonyms for undersea

Nglish: Translation of undersea for Spanish Speakers


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