sill
/sɪl/(亦作【主建筑】 cill)
noun
1- a shelf or slab of stone, wood, or metal at the foot of a window or doorway基石; 底木; 窗台; 门槛。
1.1
- a strong horizontal beam forming a base in the frame of a timber-framed building（木框架建筑的）底框梁。
1.2
- a strong horizontal member at the base of any structure, e.g. in the frame of a motor or rail vehicle（机动车或有轨车辆等的）底框梁。
1.3
- Geology a tabular sheet of igneous rock intruded between and parallel with the existing strata【地质】岩床。比较DYKE1.
1.4
- an underwater ridge or rock ledge extending across the bed of a body of water海底山脊。
词源
Old English syll, sylle 'horizontal beam forming a foundation'， of Germanic origin; related to German Schwelle 'threshold'.