gallon

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A unit of volume in the U.S. Customary System, used in liquid measure, equal to 4 quarts (3.785 liters).
2. n. A unit of volume in the British Imperial System, used in liquid and dry measure, equal to 4 quarts (4.546 liters). See Table at measurement.
3. n. A container with a capacity of one gallon.

Century Dictionary and Cyclopedia

1. n. An English measure of capacity for dry or liquid substances, but usually for liquids, containing 4 quarts. The old wine-gallon, which was declared by law to contain 231 cubic inches, and to be equal to a cylinder 7 inches in diameter and 6 inches high, is now the legal gallon of the United States, where it is taken as the volume of 8.3389 pounds avoirdupois of water at its maximum density weighed in air at 30 inches and 62° F. The imperial gallon now established in Great Britain for all liquid and dry substances contains 10 imperial pounds of distilled water at 62° F., weighed in air of the same temperature and at 30 inches. It has been ascertained to contain 277.274 cubic inches. A statute of 1266 declares that “8 pounds do make a gallon of wine, and 8 gallons of wine do make a bushel.” There was thus but one legal gallon. The pound referred to in the statute was somewhat lighter than the troy pound, but it would seem that in course of time the avoirdupois pound as substituted in practice, for the wine-gallon universally used in the latter part of the seventeenth century contained 224.4 cubic inches, while 8 avoirdupois pounds of British wine (of gooseberry or elderberry) measure about 226 inches. This wine-gallon was generally supposed, and in 1689 was legally declared, to contain 231 cubic inches, so that it was found convenient in 1707 to legalize a standard that was more accurately of this capacity. This law remains in force in the United States, though that standard has long been disused. A statute of 1452 defined the gallon as 8 troy pounds of wheat (still recognizing but one gallon), but the standard exchequer gallon constructed under Henry VII., and supposed to represent the gallon then used, contains 274 1/4 cubic inches. It was generally thought to contain 272 1/4 inches, and the statute of 1697, defining dry measures, was intended to conform to this, although it actually makes the corn-gallon 26S.6 cubic inches. Elizabeth constructed a standard gallon of 282 cubic inches (or nearly 8 pounds avoirdupois of wheat), which became the old ale-gallon. The Irish gallon, which from 1450 to 1695 had contained 8 pounds troy of wine, was at the latter date carried to 272 1/4 cubic inches; but in 1735 it was again changed to 217.1 cubic inches for all purposes. The Scotch gallon was no less than 840 cubic inches. The United States gallon is equivalent to 3.7853 liters. Abbreviated gal.
2. n. A measure of land. A gallon of land is supposed to have been the amount of land proper to sow a gallon of grain in.
3. n. The butter-bur or butterdock, Petasites Petasites.

Wiktionary

1. n. A unit of volume, equivalent to eight pints
2. n. UK exactly 4.54609 liters; an imperial gallon
3. n. US 231 cubic inches or approximately 3.785 liters for liquids (a "U.S. liquid gallon")
4. n. US one-eighth of a U.S. bushel or approximately 4.405 liters for dry goods (a "U.S. dry gallon").
5. n. in the plural, informal A large quantity (of any liquid).

GNU Webster's 1913

1. n. A measure of capacity, containing four quarts; -- used, for the most part, in liquid measure, but sometimes in dry measure.

WordNet 3.0

1. n. a British imperial capacity measure (liquid or dry) equal to 4 quarts or 4.545 liters
2. n. United States liquid unit equal to 4 quarts or 3.785 liters