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.

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). Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for sills

Historical Examples of sills

  • Some of the people had edged to the walls as if to listen, and a few had clambered to the sills as if to see.

    The Manxman

    Hall Caine

  • Indeed, a legend runs that these sills were not laid by men at all, but by the Dwarfs.

    Dwellers in the Hills

    Melville Davisson Post

  • It is used at the corners of sills and plates, also sometimes in chair-seats.

    Handwork in Wood

    William Noyes

  • On those were laid the sills, and before noon the building was up and half covered.

    Field and Forest

    Oliver Optic

  • The only external alteration he had made had been the lowering of the sills of the windows.

    The Wonder

    J. D. Beresford

British Dictionary definitions for sills


  1. Beverley, original name Belle Silverman. 1929–2007, US soprano: director of the New York City Opera (1979–89)


  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

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 sills



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.

Online Etymology Dictionary, © 2010 Douglas Harper

sills in Science


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