Definition of "sill" [sill]

• The horizontal member that bears the upright portion of a frame, especially the horizontal member that forms the base of a window. (noun)
• Geology An approximately horizontal sheet of igneous rock intruded between older rock beds. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Wolf, if you look real quickly over my shoulder, perhaps you see what they call the sill plates that help to hold up these decks, these porches that they call them here in Chicago."
• "Apart from the floor and a writing desk, every horizontal surface, including the window sill, is stacked a foot high with files and reports."
• "There was a dining chair placed in front of the sill, as if the sill was a desk."