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.
by Edward Rice May 3, 2008