high seas

Collins Concise English Dictionary © HarperCollins Publishers::

high seas noun:plural

1. (sometimes singular) the open seas of the world, outside the jurisdiction of any one nation

WordReference Random House Learner's Dictionary of American English © 2025

ˈhigh ˈsea, n. 

1. Usually, high seas. [plural* usually: the + ~] the open sea or ocean, esp. beyond the territorial waters of a country.

WordReference Random House Unabridged Dictionary of American English © 2025

high′ sea′, 

1. Nautical, Naval Terms the sea or ocean beyond the three-mile limit or territorial waters of a country.
2. Usually, high seas. 
   • the open, unenclosed waters of any sea or ocean;
     common highway.
   • Law the area within which transactions are subject to court of admiralty jurisdiction.
• bef. 1100; Middle English; Old English hēah-sǣ
high′-sea′, adj.