noun
A straight-bladed sword traditionally associated with ninja, often shorter than a katana and with a square guard.
忍者刀は、忍者が使っていたとされる刀です。
The ninja sword is a sword said to have been used by ninja.
忍刀 is another term for a ninja sword, often used interchangeably with 忍者刀.
Compound of 忍者 (ninja) and 刀 (sword). The exact historical origin of the weapon is uncertain, but it is popularly associated with ninja in modern culture.