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See more synonyms for sill on Thesaurus.com
  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.
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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
Related formssill-like, adjectiveun·der·sill, noun


  1. Mount, a mountain in E central California, in the Sierra Nevada Mountains. 14,153 feet (4314 meters).
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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words for sill

rim, ridge, berm, sill, girder, scaffolding, joist, shaft, pillar, pole, plank, timber, brink, verge, bar, reef, mantle, track, route

Examples from the Web for sill

Contemporary Examples of sill

Historical Examples of sill

  • "You let me step in," answered Mattie, a determined foot on the sill.

    Tiverton Tales

    Alice Brown

  • Presently the rod must have tapped the sill, with such a start did she face about.

    The Cavalier

    George Washington Cable

  • In a moment he had slipped over the sill and stood upon the porch.

  • She put her elbows on the sill of the window and rested her face in her hands.

    A Spirit in Prison

    Robert Hichens

  • I'll get on the sill and see what I can do through the top o' the window.

    The Burning Spear

    John Galsworthy

British Dictionary definitions for sill


  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
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Word Origin for sill

Old English syll; related to Old Norse svill sill, Icelandic svoli tree trunk, Old High German swella sill, Latin solum ground
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

Word Origin and History for sill


Old English syll "beam, threshold, large timber serving as a foundation of a wall," from Proto-Germanic *suljo (cf. Old Norse svill, Swedish syll, Danish syld "framework of a building," Middle Low German sull, Old High German swelli, German Schwelle "sill"), perhaps from PIE root *swel- (3) "post, board" (cf. Greek selma "beam"). Meaning "lower horizontal part of a window opening" is recorded from early 15c.

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Online Etymology Dictionary, © 2010 Douglas Harper

sill in Science


  1. A sheet of igneous rock intruded between layers of older rock. See illustration at batholith.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.