Definition of "ninja"

The men... are now learning to be ninja or ‘stealers-in’.

1964, Ian Fleming, You Only Live Twice, page 126

Spies prowled Japan from the seventh century, but the secretive ninja left few written records.

2000 October 15, Denver Post, page 10

Halo 2 is a lot like Halo 1, only it's Halo 1 on fire, going 130 miles per hour through a hospital zone, being chased by helicopters and ninjas. And, the ninjas are all on fire, too.

2004 July 7, Will Tuttle, quoting Jason Jones, “Halo 2 - Everything We Know!”, in GameSpy.com‎, archived from the original on 10 November 2021

For months the Japanese spoke of national-security adviser Henry Kissinger as a ninja—the magician of Japanese legends who performs supernatural acts and practices sorcery.

1972 September 11, Newsweek, Int'l ed., p. 28

Other bankers are dubbing themselves ninja, modern-day descendants of the superspies of 17th century samurai houses.

1987 August 3, Business Week, page 40

Young banking and securities firms executives (nicknamed the ninja...) are especially assigned to cultivate relations with the finance ministry. Only verbal instructions are ever given to the ninja.

1991 August 4, The Guardian, page 13

A JavaScript ninja should write lots of code and build things!

2017, Darren Jones, JavaScript: Novice to Ninja‎, SitePoint

He immediately suspected they were ninjas because, he said, they were dressed in black and wore masks, trademarks of the mysterious assassins who have been sowing terror across East Java in recent months.

1998 December 28, Chicago Tribune, page 1

Yen buyers were more subdued... fearing the Bank of Japan's new strategy of covert intervention to buy U.S. dollars through agent banks—described by some as the central bank's ninjas or secret agents.

2003 February 21, Business Times:

Many were former nomads, but as the gold rush gathered pace, students, vets and taxi drivers from Ulan Bator joined the ninjas, not just in Ogoomor but in other gold towns across the country.

2007 October 10, Jonathan Watts, “Prospectors and 'Ninja' Miners Flood to East's El Dorado”, in The Guardian

What's up, ninjas?

2003, Steven Ayromlooi, Leprechaun: Back 2 tha Hood, spoken by LEPRECHAUN

The July 1966 issue had a cartoon concerning a Ninja dojo.

1966 October, Black Belt, page 5

One of the most controversial characters in Japan's current ninja boom is a stout but surprisingly agile man in his mid-forties named Norihiro Iga-Hakuyusai.

1971 May, Black Belt, page 40

[…] Federal agents in body armor and black ninja uniforms […]

1995 August 28, Time, page 36

As they broke camp, the teenage son practised his Ninja moves with a tentpole.

2002 August 31, The Guardian, page 2

I leapt up, ninja'd over to Gav's bed and wheeched the duvet off.

1992, Iain Banks, Crow Road, page 160

In our dark house we were ninja-ing around with water guns.

1996 April 23, Rocky Mountain News, page 5

I ninja'd my way into Kung Fu Records to hang out with those merry pranksters the Vandals.

2002 August 29, Los Angeles Times, page 48