Definitions of sill
  1. noun
    structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure
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    doorsill, doorstep, threshold
    the sill of a door; a horizontal piece of wood or stone that forms the bottom of a doorway and offers support when passing through a doorway
    the sill of a window; the horizontal member at the bottom of the window frame
    type of:
    structural member
    support that is a constituent part of any structure or building
  2. noun
    (geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock
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    type of:
    rock, stone
    a lump or mass of hard consolidated mineral matter
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