undersea

1 of 2

adjective

un·​der·​sea ˌən-dər-ˈsē 

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

undersea

2 of 2

adverb

variants or underseas

ˌən-dər-ˈsēz 

: 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

But other countries also depend heavily on the region’s undersea cable network—one third of India’s westbound Internet traffic goes through the Persian Gulf and Strait of Hormuz. — Jeremy Hsu, ArsTechnica, 6 Nov. 2026

These systems are optimized for combat-ready maritime patrol in detecting, locating and tracking surface and undersea targets. — Prabhat Ranjan Mishra, Interesting Engineering, 5 Nov. 2026

Last year, attacks on undersea cables in Eastern Europe’s Baltic Sea, allegedly linked to Russia, disrupted connectivity in Sweden and Latvia, prompting calls from telecom firms for governments to step in. — Will McCurdy, PC Magazine, 24 Oct. 2026

Iranian officials have vowed to widen their attacks to target data centers and undersea internet cables, while refusing concessions on their nuclear program. — Anniek Bao, CNBC, 22 Oct. 2026

Word History

First Known Use

Adjective

1613, in the meaning defined at sense 1

Adverb

1645, in the meaning defined above

Rhymes for undersea

• abc
• absentee
• addressee
• adoptee
• allottee
• amphorae
• amputee
• apc
• apogee
• appointee
• assessee
• assignee

Kids Definition

undersea

adjective

un·​der·​sea

ˈən-dər-ˈsē

1

: being or carried on under the sea or under the surface of the sea

undersea oil deposits

undersea warfare

2

: designed for use under the surface of the sea

undersea fleet