structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure
"The carpenter replaced the rotted sill at the bottom of the window frame to prevent further water damage."
(geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock
"Geologists identified a thick sill intruding horizontally through the ancient shale and limestone beds during their field study."
(also window sill) breast wall; window breast; horizontal brink which forms the base of a window.
"The old horse drew its load firmly against the wooden sill as it pulled up to the market gate."
A young herring.
The shaft or thill of a carriage.
A surname.
"The Sill family has lived in our neighborhood for three generations."
The word "sill" comes from Old English syll, meaning a threshold or foundation. It traces its roots back to the Proto-Indo-European concept of a beam or frame.