A symbol used in the natural gas industry for 1000 (not one million) cubic feet of gas equivalent (cfe). This is really an energy unit equal to about 1.091 gigajoules (GJ)
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}