The specific term for a ninja's sword is not distinct in historical sources or traditional Japanese terminology. Ninjas, also known as shinobi, were covert agents and spies in feudal Japan who employed a wide range of weapons and tools based on the mission and circumstances.

While ninjas did use swords on occasion, they typically utilized common swords available during their time, such as the katana or wakizashi, which were also used by samurai warriors. The choice of sword would depend on the situation and the individual ninja's preferences or access to weapons.

In popular culture and fictional depictions, the term "ninja sword" is often used to describe shorter, straight-bladed swords or unique weapon designs associated with ninjas. However, these designs are largely products of imagination and creative interpretation rather than reflecting historical accuracy.

It's important to note that the emphasis of ninjas was on stealth, espionage, and unconventional warfare, rather than wielding a specific type of sword. Their expertise encompassed a wide range of skills, including espionage, sabotage, guerrilla warfare, disguise, and various weapon techniques.

In summary, while the term "ninja sword" is commonly used in popular culture, there is no specific term or dedicated type of sword exclusively attributed to ninjas in historical sources or traditional Japanese terminology. The swords they used were similar to those employed by samurais of their time.