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Sill

[sil]
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

British Dictionary definitions for mount-sill

sill

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
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Word Origin

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 mount-sill

sill

n.

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

mount-sill in Science

sill

[sĭl]
  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.