sill

Definition

A flat horizontal piece at the bottom of a door or window; also, in geology, a sheet of igneous rock that has intruded between older rock layers.

中文 门或窗底部的平坦水平部分；在地质学中，指入侵到较老岩层之间的火成岩层。

Example

"He wiped his boots on the doorstep before stepping over the sill."