Aboideau
The Century Dictionary and Cyclopedia
noun.
A dam to prevent the tide from overflowing a marsh.
To improve (a tidal river or stream) and prevent the tidal overflow of its marshes and tidal meadows by placing tide-gates at its mouth.
Wiktionary, Creative Commons Attribution/Share-Alike License
noun.
A
tide
gate
, designed to protect
marshland
, so constructed as to let out water at low tide, but to prevent an influx of water at high tide.