windowsill
/ˈwɪndəʊˌsɪl
/noun
A ledge or sill forming the bottom part of a window.Well, the caulking would go down here with the window sill, with the frame....
- Keep a bucket of soapy water and a second sponge to clean the exterior window sill.
- It is thought he climbed to the window sill and then slipped over the ledge.