wash sale
n.— «If you sell, make sure you don’t run afoul of what’s known as the wash-sale rule. A wash sale happens when you sell a security at a loss and, within 30 days before or after the sale, you buy the same thing, or something “substantially identical.” In that case, you can’t deduct your loss.» —“Tax Advantages of Dumping a Losing Stock” by Tom Herman Wall Street Journal July 29, 2007. (source: Double-Tongued Dictionary)