Gallon \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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Imperial \Im*pe"ri*al\, a. [OE. emperial, OF. emperial, F. imp['e]rial, fr. L. imperialis, fr. imperium command, sovereignty, empire. See Empire.]

1. Of or pertaining to an empire, or to an emperor; as, an imperial government; imperial authority or edict.

The last That wore the imperial diadem of Rome. --Shak.

2. Belonging to, or suitable to, supreme authority, or one who wields it; royal; sovereign; supreme. ``The imperial democracy of Athens.'' --Mitford.

Who, as Ulysses says, opinion crowns With an imperial voice. --Shak.

To tame the proud, the fetter'd slave to free, These are imperial arts, and worthy thee. --Dryden.

He sounds his imperial clarion along the whole line of battle. --E. Everett.

3. Of superior or unusual size or excellence; as, imperial paper; imperial tea, etc.

Imperial bushel, gallon, etc. See Bushel, Gallon, etc.

Imperial chamber, the, the sovereign court of the old German empire.

Imperial city, under the first German empire, a city having no head but the emperor.

Imperial diet, an assembly of all the states of the German empire.

Imperial drill. (Manuf.) See under 8th Drill.

Imperial eagle. (Zo["o]l.) See Eagle.

Imperial green. See Paris green, under Green.

Imperial guard, the royal guard instituted by Napoleon I.

Imperial weights and measures, the standards legalized by the British Parliament.

Source: Webster's Revised Unabridged Dictionary (1913)