The term shinobi (kanji: 忍) means "ninja [literally stalking or hiding]" in English. It is written しのび in hiragana. It's pronounced roughly like "she-know-bee".
Another word for ninjaNINJA 忍者 "stalking/hiding person" learn more.... In the Chinese reading, 忍 is nin (the same nin in ninja) and means stalking around or hiding. The infinitive form of shinobi as a verb is shinobu, 忍ぶ. In more common usage, it means to endure suffering and hardship, especially in a stoic manner.
Incidentally, Shinobu is a girl’s name. (It can be a boy’s name, too, even if the chance of a misunderstanding can be high.)