A metric unit of mass or weight equal to one billion metric tons (tonnes) or about 2.2046 trillion pounds. This very large unit is used, for example, in discussing the amounts of carbon added to the atmosphere by human activities
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}