crossjack
/ˈkrɔsˌdʒæk/
noun
- A square sail set on the lower yard of the mizzenmast on a sailing ship.
- During the storm, the crossjack was reefed to prevent damage to the mast.
- The sailors unfurled the crossjack to catch the wind from the stern.
- The old ship's crossjack was made of heavy canvas and reinforced with rope.