[groin] n [alter. of ME grynde, fr. OE, abyss; akin to OE grund ground] (ca. 1532) 1: the fold or depression marking the juncture of the lower abdomen and the inner part of the thigh; also: the region of this line
2. a: the projecting curved line along which two intersecting vaults meet b: a rib that covers this edge
3: 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
[2]groin vt (ca. 1816): to build or equip with groins