GROIN

I. noun Etymology: alteration of Middle English grynde, from Old English, abyss; akin to Old English grund ground Date: circa 1532 the fold or depression marking the juncture of the lower abdomen and the inner part of the thigh, 2. the projecting curved line along which two intersecting vaults meet, a rib that covers this edge, a rigid structure built out from a shore to protect the shore from erosion, to trap sand, or to direct a current for scouring a channel, II. transitive verb Date: circa 1816 to build or equip with ~s