GROIN (3)

Groin, n. [[Icel. grein distinction, division, branch; akin to Sw. gren, branch, space between the legs, Icel. greina to distinguish, divide, Sw. grena to branch, straddle. Cf. Grain a branch.]] 1. 1. (Anat.) The line between the lower part of the abdomen and the thigh, or the region of this line; the inguen.
2. 2. (Arch.) The projecting solid angle formed by the meeting of two vaults, growing more obtuse as it approaches the summit.
3. 3. (Math.) The surface formed by two such vaults.
4. 4. A frame of woodwork across a beach to accumulate and retain shingle. Weale.