Narrow, roughly shore-normal structure built to reduce longshore currents, and/or to trap and retain beach material Most groynes are of timber or rock, and extend from a sea wall, or the backshore, well onto the foreshore and rarely even further offshore In the USA and historically called a groin
[ 'groin ] (noun.) 1582. From Old French groign from late Latin grunium, grunia, from mediæval Latin grunnium ‘snout’, from Latin grunnire ‘grunt like a pig’.