A traditional symbol for one million Btu (about 1.055 057 gigajoules (GJ)), a unit used widely in the energy industry. This unit is also called the dekatherm
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}