From The Collaborative International Dictionary of English v.0.48 :
Groyne \Groyne\, n. [Obs.]
See Groin.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
groyne
n 1: a protective structure of stone or concrete; extends from
shore into the water to prevent a beach from washing away
[syn: breakwater, groin, groyne, mole, bulwark,
seawall, jetty]