Rounding-up is a phenomenon that occurs in sailing

Sailing

Sailing is the propulsion of a vehicle and the control of its movement with large foils called sails. By changing the rigging, rudder, and sometimes the keel or centre board, a sailor manages the force of the wind on the sails in order to move the boat relative to its surrounding medium and...

 when the helmsman

Helmsman

A helmsman is a person who steers a ship, sailboat, submarine, or other type of maritime vessel. On small vessels, particularly privately-owned noncommercial vessels, the functions of skipper and helmsman may be combined in one person. On larger vessels, there is a separate officer of the watch,...

 (or tiller

Tiller

A tiller or till is a lever attached to a rudder post or rudder stock of a boat that provides leverage for the helmsman to turn the rudder...

-handler) is no longer able to control the direction of the boat and it heads up (or "rounds up") into the wind, causing the boat to slow down or stall out. This occurs when the wind

Wind

Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

 overpowers the ability of the rudder

Rudder

A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

 to maintain a straight course. For example, the sailboat

Sailboat

A sailboat or sailing boat is a boat propelled partly or entirely by sails. The term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined and what constitutes a sailing ship, sailboat, or a...

 may heel over so far that the rudder no longer engages in the water, or only to such a small extent that it can no longer steer the boat. When this happens is dependent on a number of factors such as the velocity of the wind, design of the sailboat hull and rudder and shape of the sails. While not usually dangerous, the occurrence of rounding up can be startling to the skipper or helmsman of the boat. The boat turns into the eye of the wind with all sails fluttering. However, once the boat has rounded up and lies into the wind, control can be readily regained by steering the boat off the wind to refill the sails with wind and regain the desired course. Rounding-up is in fact a safety design of most sailboats that can help prevent a knock-down and allow the helmsman to regain control of the boat. An occasional round-up may simply be the result of a strong gust of wind. If it occurs regularly, this may be a sign that too much sail is raised and the crew may need to lower one or more sails, change to smaller sails, or reef

Reefing

Reefing is a sailing manoeuvre intended to reduce the area of a sail on a sailboat or sailing ship, which can improve the ship's stability and reduce the risk of capsizing, broaching, or damaging sails or boat hardware in a strong wind...

 in the mainsail

Mainsail

A mainsail is a sail located behind the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast....

. In smaller sailboats such as a Sunfish

Sunfish (dinghy)

The Sunfish sailboat is a personal size, beach launched sailing dinghy utilizing a pontoon type hull carrying a lateen sail mounted to an un-stayed mast....

 or Laser

Laser (dinghy)

The International Laser Class sailboat, also called Laser Standard and the Laser One is a popular one-design class of small sailing dinghy. According the Laser Class Rules the boat may be sailed by either one or two people, though it is rarely sailed by two. The design, by Bruce Kirby, emphasizes...

 where the sail cannot be lessened or reefed, frequent round-ups may be a sign that the wind conditions are becoming too strong for the boat, such as anything approaching a Small Craft Exercise Caution

Small craft advisory

A small craft advisory is a type of warning issued by the National Weather Service in the United States, most frequently in coastal areas. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force....

condition, and the sailor(s) should immediately proceed to shelter.