a horizontal piece of wood, metal, etc, e.g. a timber, that forms the lowest member, or one of the lowest members, of a framework or supporting structure, e.g. a window frame or door frame
a narrow shelf projecting from the base of a window frame, esp inside a room
in geology, a horizontal sheet of intrusive igneous rock running between strata of other rocks
a submerged ridge at relatively shallow depth separating two deeper bodies of water
[Old English syll]