sill
1 Americannoun
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a horizontal timber, block, or the like serving as a foundation of a wall, house, etc.
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the horizontal piece or member beneath a window, door, or other opening.
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Geology. a tabular body of intrusive igneous rock, ordinarily between beds of sedimentary rocks or layers of volcanic ejecta.
noun
noun
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a shelf at the bottom of a window inside a room
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a horizontal piece along the outside lower member of a window, that throws water clear of the wall below
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the lower horizontal member of a window or door frame
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a continuous horizontal member placed on top of a foundation wall in order to carry a timber framework
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a flat usually horizontal mass of igneous rock, situated between two layers of older sedimentary rock, that was formed by an intrusion of magma
Other Word Forms
- sill-like adjective
- undersill noun
Etymology
Origin of sill
before 900; Middle English sille, Old English syl, sylle; cognate with Low German süll, Old Norse syll; akin to German Schwelle sill
Vocabulary lists containing sill
Earth Science - Middle School
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Earth Science - High School
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Rocks and Minerals - Middle School and High School
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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.
Video footage from inside their Riverside home showed water levels reaching just below the window sill, after the the Six Mile Water River burst its banks.
From BBC • Jan. 27, 2026
The Red Sea was initially connected from the north to the Mediterranean through a shallow sill.
From Science Daily • Oct. 8, 2025
They’re sill exploring options, including possibly lending it to the L.A.
From Los Angeles Times • Mar. 11, 2024
But this is the first time sill construction has been used in consecutive years.
From Seattle Times • Oct. 26, 2023
My mother finds me slumped in a heap by the open window in the morning, my head resting on the sill.
From "Sparrow" by Sarah Moon
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.
