AskDefine | Define sill

Dictionary Definition



1 structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure
2 (geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock

User Contributed Dictionary



From Middle English sille, from Old English syll, threshold.


  • , /sɪl/, /sIl/,
  • Rhymes with: -ɪl


  1. (also window sill) A horizontal slat which forms the base of a window.
    She looked out the window resting her elbows on the window sill.
  2. A horizontal member bearing the upright portion of a frame.
  3. A horizontal layer of igneous rock between older rock beds.

Usage notes

Usually spelled cill when used in the context of canal or river engineering.


base of a window
horizontal member bearing the upright portion of a frame
layer of igneous rock



  1. herring

See also

Extensive Definition

Sill may refer to:
  • Sill (geology), a tabular mass of igneous rock that has been intruded laterally between layers of older rock
  • In construction terminology:
    • In architecture, a sill is the bottom edge of a window or door
    • In building construction, the bottom horizontal member of a wall or building to which vertical members are attached is called a sill plate. (This is also, confusedly, sometimes also called the sill.)
    • The sill proper being the finished (leveled} area of a masonry or concrete foundation normally also prepared by imbedding large hold-down 'J' bolts (in concrete) or drilled for Lags (masonry or concrete) and lag bolts so the sill plate can be fastened to the foundations.
  • Sill River, a tributary to the Inn River in Austria
  • Mount Sill, a mountain peak in California's Sierra Nevada range
  • When magma squeezes between horizontal layers of rock, forms sill.
  • In automobiles, a sill is a box section of metal (normally steel) which maintains the door gap and provides torsional strength in the body of a car. it normally comprises both an inner, and an outer section which when put together, creates a strong box section. On cars which use monocoque construction, as opposed to a frame chassis, the sill becomes one of the main components providing strength in the body.


See also

sill in Dutch: Sill
sill in Polish: Sill

Synonyms, Antonyms and Related Words

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