A unit used in the paper industry to express the weight (really, the thickness) of paper. The basis weight is the weight in pounds of one ream (500 sheets) of a basic size sheet. For details, see pound weight
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}