Definition of Sill:
- A submerged bar blocking partially the mouth of a river, a harbour or an estuary.
- Submerged shore-parallel dike built for the purpose of reducing wave activity at its leeside; the more usual term in this case is submerged breakwater or artificial reef.
- Submerged shore-parallel dike built as support of a perched beach at the seaside.
- Tabular sheet that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or along the direction of foliation in metamorphic rock .
This is the common definition for Sill, other definitions can be discussed in the article