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Synonyms

sill

1 American  
[sil] / sɪl /

noun

  1. a horizontal timber, block, or the like serving as a foundation of a wall, house, etc.

  2. the horizontal piece or member beneath a window, door, or other opening.

  3. Geology. a tabular body of intrusive igneous rock, ordinarily between beds of sedimentary rocks or layers of volcanic ejecta.

Sill 2 American  
[sil] / sɪl /

noun

  1. Mount, a mountain in E central California, in the Sierra Nevada Mountains. 14,153 feet (4,314 meters).

sill British  
/ sɪl /

noun

  1. a shelf at the bottom of a window inside a room

  2. a horizontal piece along the outside lower member of a window, that throws water clear of the wall below

  3. the lower horizontal member of a window or door frame

  4. a continuous horizontal member placed on top of a foundation wall in order to carry a timber framework

  5. a flat usually horizontal mass of igneous rock, situated between two layers of older sedimentary rock, that was formed by an intrusion of magma

"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
sill Scientific  
/ sĭl /

  1. A sheet of igneous rock intruded between layers of older rock.

  2. See illustration at batholith

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

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

“It’s the law,” the not-unkind super replies — though Alex, now 2, can barely sit up, let alone reach the sill.

From New York Times • Apr. 23, 2024

This rigid material must be custom cut and fit tight between the floor joists, subfloor and sill plate.

From Seattle Times • Apr. 1, 2024

I swung my feet from the sill to the fringes of the rug.

From "The Light in Hidden Places" by Sharon Cameron

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.