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porthole

American  
[pawrt-hohl, pohrt-] / ˈpɔrtˌhoʊl, ˈpoʊrt- /

noun

  1. a round, windowlike opening with a hinged, watertight glass cover in the side of a vessel for admitting air and light.

  2. an opening in a wall, door, etc., as one through which to shoot.

porthole British  
/ ˈpɔːtˌhəʊl /

noun

  1. Sometimes shortened to: port.  a small aperture in the side of a vessel to admit light and air, usually fitted with a watertight glass or metal cover, or both

  2. an opening in a wall or parapet through which a gun can be fired; embrasure

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of porthole

First recorded in 1585–95; port 4 + hole

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.