- a member of the ninja who were trained in martial arts and hired for espionage or sabotage or assassinations; a person skilled in ninjutsu
- a class of 14th century Japanese who were trained in martial arts and were hired for espionage and assassinations
- He's a ninja.
- Ninja Turtles is my favorite game.
- Let's make believe we are ninja.
- My older sister is a female ninja.
- I saw a man dressed like a ninja.
- He was like a ninja hiding behind one of our cars!
- Kamui no Ken was a sort of samurai/ninja story set during the transition of the fall of the Tokugawa Shogunate and the re-establishment of Japan under the Emperor Meiji in 1868.