"1000 denier", "1600 denier", etc, appears a lot in tactical clothing. It's a measure of density, which is itself a measure of weight. A one-denier piece of fabric has one gram of weight per 9000 meters (9km). 1600 denier fabric would have a weight of 1600 grams, or 1.6kg, in a single 9000-meter strand.
-- SeanNewton - 11 Nov 2009