1. Abbreviated gal.

2. A unit of volume used in the United States for measurement of liquid substances, equal to 231 cubic inches, or to 3.785 411 784 × 10^-3 cubic meter, or to 3.785 411 784 liters; equal to 128 fluid ounces.

3. A unit of volume used in the United Kingdom for measurement of liquid and solid substances, usually the former; equal to the volume occupied by 10 pounds of weight of water of density 0.998859 gram per milliliter in air of density 0.001217 gram per milliliter against weights of density 8.136 grams per milliliter (the milliliter here has its old definition of 1.000028 × 10^-6 cubic meter); approximately equal to 277.420 cubic inches, or to 4.54609 × 10^-3 cubic meter, or to 4.54609 liters; equal to 160 fluid ounces. Also known as imperial gallon.