A 'shinobi' is a term originating from Japan, often used interchangeably with 'ninja'. Shinobi were covert agents who took on roles as mercenaries during feudal Japan. These skilled agents were experts in unconventional warfare tactics including but not limited to espionage, sabotage, and guerrilla warfare.
A shinobi's role was to create confusion among the enemy, collect intelligence and perform assassinations if necessary. They're heavily featured in Japanese pop culture, especially in manga and anime, like 'Naruto', where the characters live in a modern shinobi world.