Which term describes the process of reducing sail area on a vessel?

The term that describes the process of reducing sail area on a vessel is "reef." Reefing involves adjusting a sail to make it smaller, typically by folding or rolling part of the sail, to allow the boat to handle stronger winds safely. This is an essential skill in sailing, as it helps maintain control and prevents excessive heeling or potential damage to the vessel and its rigging when wind conditions become too strong for full sail.

Although the other terms relate to aspects of sail handling, they do not specifically pertain to reducing the sail area in the same way. "Furl" refers to rolling or folding a sail around its mast or boom, which can also reduce the sail area but is often more associated with storing sails away when not in use. "Flake" is the process of folding a sail neatly for storage, and "haul" typically refers to the act of pulling on a line or halyard. Thus, reefing is distinct in its purpose and execution, making it the correct choice for this specific process.