- a heavy, horizontal timber or line of masonry supporting a house wall, etc.
- a horizontal piece forming the bottom frame of the opening into which a window or door is set
- Geol. a flattened piece of igneous rock forced between beds of stratified rocks
Origin of sillMiddle English sille from Old English syll, akin to Danish sville, German schwelle from Indo-European base an unverified form sel-, an unverified form swel-, beam, plank from source Classical Greek selma, beam