A traditional unit of volume equal to about 1.201 U.S. liquid gallon or 4.546 liters. See: Gallon [3]. In Canada, the term "Imperial" is used frequently to distinguish the British Imperial units from the corresponding U.S. units
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}