Shuriken ("sword hidden in the hand") is a traditional Japanese concealed weapon that were generally used for throwing, and sometimes for stabbing or slashing. They are sharpened hand-held blades made from a variety of everyday items such as needles, nails, and knives, as well as coins, washers, and other flat plates of metal.
Shuriken are commonly known in the West as "ninja throwing stars", though they took many different shapes and designs during the time they were used. Shuriken were mainly a supplemental weapon to the more commonly used katana (sword) or yari (spear) in a warrior's arsenal, though they often played a pivotal tactical role in battle.
Contrary to popular belief, shuriken were not primarily intended as a killing weapon, but rather as a secondary weapon that sometimes played a role supportive to a warrior's main weapon, usually the sword or spear, but it could be deadly in the hands of a skillful shinobi. Shuriken were primarily used to cause either nuisance or distraction, both being tactics to gain an advantage in battle. Targets were primarily the eyes, face, hands, or the feet, the areas most exposed by a samurai's armor. The shuriken would also sometimes be thrown in a way that cuts the opponent and become lost later, causing the opponent to believe that they were cut by an invisible swordsman.
Shuriken, especially hira-shuriken, were also used in other novel ways – they might be embedded in the ground, injuring those who stepped on them, or wrapped in fuse to be lit and thrown to cause fire. They can also be used as a handheld striking weapon in close combat. There are reports of shuriken being coated with poison intended either for a throwing target or for whoever may pick them up when left in a conspicuous place.