This is really just another word for Ninja.
Sega commonly referred to as the Shinobi series. The name Shinobi is used as a code-name throughout the series to hide the true identity of its bearer. It has been adopted by various characters, most prominently Joe Musashi, the protagonist of the original series of games (Shinobi -- Shinobi III).
Shinobi is a video game in the Shinobi series, developed and published by Sega for Sega Game Gear. It was released in 1991 as an exclusive game to the Game Gear console. Alternatively, it is known as The Game Gear Shinobi or (abbreviated) The GG Shinobi.