1. (n.) The basis or foundation of a thing; especially, a horizontal piece, as a timber, which forms the lower member of a frame, or supports a structure; as, the sills of a house, of a bridge, of a loom, and the like.

2. (n.) The timber or stone at the foot of a door; the threshold.

3. (n.) The timber or stone on which a window frame stands; or, the lowest piece in a window frame.

4. (n.) The floor of a gallery or passage in a mine.

5. (n.) A piece of timber across the bottom of a canal lock for the gates to shut against.

6. (n.) The shaft or thill of a carriage.

7. (n.) A young herring.

base basement basis bearing wall bed bedding bedrock doorsill doorstone floor flooring fond footing foundation fundament fundamental ground grounds groundsel groundwork hardpan mudsill pavement principle radical riprap rock bottom rudiment seat solid ground solid rock stereobate stylobate substratum substruction substructure terra firma threshold underbuilding undercarriage undergirding underpinning understruction understructure window sill