A cutlass sword is a slightly curved, broad short sword. They are most well-known from the classic 19th century style used on ships. Often they feature hilts that have cupped guards, and decorative wrapped handles. They feature both a slight stabbing point and a sharpened cutting edge, and are substantial and weighty weapons.
The name, cutlass sword, itself derives from the Latin cultellus, a form of culter, which was a plowshare. From Latin it came through the French and into Italian as coltellaccio, a form of the word for knife. The cutlass sword is also sometimes known as the curtal axe, curtelaxe, or curtelace. All of these terms refer to the exact same weapon, and were simply different historical words used to describe the cutlass sword.
In the world of naval warfare, especially, the cutlass sword has often been seen historically. The cutlass sword in this context is often referred to simply as the naval side arm, and was the weapon most often seen on a sailor through the 17th, 18th, and 19th centuries. The cutlass makes for an ideal side arm on a ship for a number of reasons, relating to its size, weight, and simplicity.
Firstly, its heft and sharp edge made it an ideal implement outside of combat, for cutting through canvas sheets, thick ropes, and even wood. Secondly, its short length made it perfect for fighting in the often cramped quarters of a ship, or in the rigging. And lastly, unlike the rapier, the cutlass required relatively little training to use well, making it perfect for sailors whose lives were not dedicated to fighting.
When most people think of the cutlass sword, they actually think of pirates. As early as the mid-17th century pirates were using cutlasses as their weapon of choice, and they soon became iconically connected to the pirate lifestyle. The very simplicity of a cutlass made them perfectly suited to the pirate way of combat, as well as their overall demeanor. Simple weapons, meant to get the job done, whether the job was cutting rope or cutting down enemies, the cutlass fit the pirate mystique.
Eventually the cutlass became less and less popular as a weapon among seamen, as swords themselves gave way to firearms. Their use held out far longer than swords on land, however, likely because of the constant worry about wet powder and the need for a backup weapon. As late as 1935 the British Royal Navy was still using the cutlass in landing parties, and in the United States Navy soldiers were still carrying the 1917 model cutlass during World War II.
On land, the cutlass is perhaps best associated with the Ottoman Empire. The cutlass sword was widely used by Ottoman cavalry, especially Mamluks, who were often not allowed to carry weapons. Because of their use as an agricultural implement and general tool, cutlasses were often allowed to be carried in the Ottoman Empire, even during times of peace when weapons would normally be withheld from the Ottoman slave soldiers.