American Dictionary of the English Language

CROTCH, noun [See Crook and Crutch.]

1. A fork or forking; the parting of two legs or branches; as the crotch of a tree.

2. In ships, a crooked timber placed on the keel, in the fore and aft parts of a ship.

3. A piece of wood or iron, opening on the top and extending two horns or arms, like a half moon, used for supporting a boom, a spare topmast, yards, etc.