ninjutsu
/nɪnˈdʒʌtsuː/noun
mass noun
- the traditional Japanese technique of espionage, characterized by stealthy movement and camouflage. It was developed in feudal times for military purposes and subsequently used in the training of samurai.忍术（以秘密行动和伪装为特点的日本传统间谍技术, 发展于日本封建时期, 原用于军事目的, 后用于训练武士）。
词源
Japanese, from nin 'stealth' + jutsu 'art, science'.