er bai wu, pronounced AR-BUY-OO in Mandarin Chinese, is translated literally as the number 250 and is a slang term for a very, VERY stupid person. This is widely used in the Northeastern region of China and treated as a taboo with a great deal of superstition. The number is avoided whenever possible, if a buyer in a market is bargaining, he would offer 249 or 251 yuan for an item, but never 250 for risk of appearing foolish.
Every student in that friggin class is er bai wu.
by Edward Rice May 02, 2008