watertight
Americanadjective
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constructed or fitted so tightly as to be impervious to water.
The ship had six watertight compartments.
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so devised or planned as to be impossible to defeat, evade, or nullify.
a watertight contract; a watertight alibi.
adjective
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not permitting the passage of water either in or out
a watertight boat
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without loopholes
a watertight argument
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kept separate from other subjects or influences
different disciplines are often thought of in watertight compartments
Other Word Forms
Etymology
Origin of watertight
Middle English word dating back to 1350–1400; see origin at water, tight
Explanation
When something is watertight, it's sealed so securely that no liquid can get in or out. If your goggles aren't watertight, your eyes will sting after your swimming lesson. The porthole windows in the side of a cruise ship have to be watertight so no water gets in during storms and the ship continues to float, rather than sinking. And when you brave the flume ride at a local amusement park, you might want to seal your wallet in a watertight pouch. Figuratively, something watertight stands up to any possible questions or doubts: "Her alibi is watertight — her grandma swears they were baking cookies all day."
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
It wasn’t watertight, which allowed water to seep in and damage the concrete, the complaint said.
From The Wall Street Journal • Jul. 10, 2026
The unmoving, shallow water can’t help but grow algae in the beating sun, and since the concrete expands and contracts with shifting temperatures, any seals along the seams have struggled to remain watertight.
From Slate • Jun. 19, 2026
The crew needed a watertight soundstage for that scene, so they savvily constructed the set in the school’s empty pool, where overflowing water would not be an issue.
From MarketWatch • Dec. 29, 2025
The crash should have flooded just two of the boat's six watertight compartments, but a missing door meant that three were compromised, dooming the vessel.
From Barron's • Dec. 2, 2025
For the first time in human experience, people now had watertight containers readily available in any desired shape.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
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.
