(1) A submerged ridge at relatively shallow depth separating the basins of two bodies of water. (2) A horizontal beam forming the bottom of the entrance to a lock. (3) Also, a low, submerged dam-like structure built to control riverbed scour and current speeds.
SILL
Meaning of SILL in English
Environmental engineering English vocabulary. Английский словарь экологического инжиниринга. 2012