To reef a sail is to make it smaller.
The Rig and the Standing and Running Rigging
The Rig of a boat is the gear which holds the sails in place, and controls their shape, size and angle of attack.
Glossary of Nautical Terms
A modern sailor is recruited by the Royal Navy and finds himself on the deck of HMS Impérieuse in 1813, as she sails into battle against overwhelming odds. At stake are $5 billion in gold and the fate of the modern world.