\Gal"lon\, n. [OF galon, jalon, LL. galo, galona, fr.
galum a liquid measure; cf. F. jale large bowl. Cf. {Gill} a
measure.]
A measure of capacity, containing four quarts; -- used, for
the most part, in liquid measure, but sometimes in dry
measure.
Note: The standart gallon of the Unites States contains 231
      cubic inches, or 8.3389 pounds avoirdupois of distilled
      water at its maximum density, and with the barometer at
      30 inches. This is almost exactly equivalent to a
      cylinder of seven inches in diameter and six inches in
      height, and is the same as the old English wine gallon.
      The beer gallon, now little used in the United States,
      contains 282 cubic inches. The English imperial gallon
      contains 10 pounds avoirdupois of distilled water at
      62? of Fahrenheit, and barometer at 30 inches, equal to
      277.274 cubic inches.