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 underseas (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 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, "Coronavirus is pushing more work online. Is that good for the planet?," 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, "Trump's New Intelligence Chief Spells Trouble," 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, "Giant Volcano Rewrites the Story of Seafloor Formation," 1 May 2020 They all are found amid the colorful corals and sponges and magnificent undersea formations. Chuck Yarborough, cleveland, "Bonaire: A diver’s paradise where the massive coral reef teems with sea life and beauty," 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, "The Sea Is Getting Warmer. Will the Shrimp Get Louder?," 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, "South Africans under lockdown have to deal with slow internet after another undersea cable break," 30 Mar. 2020 Space, undersea, going after undersea cables, for example, and also cyber. CBS News, "Transcript: Former top defense official Robert Work on "Intelligence Matters"," 11 Mar. 2020 That matters, because a loud party in an undersea neighborhood disrupts life for everyone else who lives there. Eric Niiler, Wired, "The Sea Is Getting Warmer. Will the Shrimp Get Louder?," 28 Feb. 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.

See More

First Known Use of undersea


1613, in the meaning defined at sense 1


1645, in the meaning defined above

Keep scrolling for more

Learn More about undersea

Time Traveler for undersea

Time Traveler

The first known use of undersea was in 1613

See more words from the same year

Statistics for undersea

Cite this Entry

“Undersea.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/undersea. Accessed 24 Nov. 2020.

Keep scrolling for more

More Definitions for undersea


How to pronounce undersea (audio)

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

Comments on undersea

What made you want to look up undersea? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

A Thanksgiving Word Quiz

  • a traditional thanksgiving dinner
  • November comes from a word for which of the following numbers?
Spell It

Can you spell these 10 commonly misspelled words?

Syn City

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!