gallon means: American units of measure equal to 128 fluidoz. sixteen cups, eight pints, or four quarts. (in Cooking Dictionary)

What else does gallon mean?

The US Customary System defines a unit of volume as a liquid measurement equal to four quarts (3.8785 liters). (in Merlin Dictionary)

The British Imperial System defines a unit of volume as a liquid or dry measurement. It is equal to 4 quarts (4.56 liters). (in Merlin Dictionary)

Container with one-gallon capacity (in Merlin Dictionary)