groyne
An often wooden structure that projects from a coastline to prevent erosion, longshore drift etc.; a breakwater.
Old rail and timber groynes will be erected along the beach to trap shingle moved by coastwise drift, and to rebuild the protection to the toe of the embankment.
Where it comes from
From Middle English groyn (“snout”), from Old French groign, from Late Latin grunium, grunia, from Latin grunnire (“grunt like a pig”).
Adapted from the Wiktionary entry groyne (CC BY-SA 4.0).