Definitions of sill

n structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure

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

n (geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock

Type of:
rock, stone
a lump or mass of hard consolidated mineral matter

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