Ninjews are rare and hard to pick out of a crowd.
1. Ninjews are mammals, and often hairy to the point of being jewbacca.
2. Ninjews fight ALL the time, except when they're drinking or bitching. A bitch-drink-fight cycle is not uncommon.
3. The purpose of the ninjew is to flip out and kill people.
B. In some circles, "Ninjew" is used to colloquially refer to Ultra-Orthodox, Haredi descendants of Abraham who roam the poorly lit back-alleys of Meah Shearim and New Square.
Man 1: Dude, this girl fights like a Ninja!
Man 2: I think the word you are looking for is "Ninjew."
Woman 1: That guy came out of nowhere, lit my house on fire, and stole my money--just because my knees and elbows were showing!
Woman 2: You have to watch out for those Ninjews.