acre

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A unit of area in the U.S. Customary System, used in land and sea floor measurement and equal to 160 square rods, 4,840 square yards, or 43,560 square feet. See Table at measurement.
2. n. Property in the form of land; estate.
3. n. A wide expanse, as of land or other matter. Often used in the plural: "Everything was streaky pink marble and acres of textureless carpeting” ( Anne Tyler).
4. n. Archaic A field or plot of arable land.

Century Dictionary and Cyclopedia

1. n. Originally. an open plowed or sowed field. This signification was gradually lost after the acre was made a definite measure of surface. Still used in the plural to denote fields or land in general.
2. n. A superficial measure of land, usually stated to be 40 poles in length by 4 in breadth; but 160 perches (= 4840 square yards, or 43,560 square feet) make an acre, however shaped. An acre, as a specific quantity of land, was reckoned in England as much as a yoke of oxen could plow in a day till the establishment of a definite measure by laws of the thirteenth century and later. This is known in Great Britain and the United States as the statute acre, to distinguish it from the customary acres still in use to some extent in Scotland, Ireland, and Wales. The Scotch acre is larger than the statute acre, as it contains 6150.4 square yards, 48 Scotch acres being equal to 61 statute acres. The Irish acre is 7840 square yards, 100 Irish acres being nearly equivalent to 162 statute acres. In Wales different measures, the erw, the stang, the paladr, are called acres. The true erw is 4320 square yards; the stang is 3240. There is also the Cornish acre, of 5760 square yards. Among the customary English acres are found measures of the following numbers of perches: 80 (of hops), 90 (of hops), 107, 110, 120 (shut acre), 130, 132, 134, 141, 180 (forest acre), 200 (for copyhold land in Lincolnshire), 212, 256 (of wood). The Leicestershire acre has 2308¾ square yards, the Westmoreland acre 6760 square yards, the Cheshire acre 10,240 square yards. Often abbreviated to A. or adjective
3. n. A lineal measure equal to a furrow's length, or 40 poles; more frequently, an acre's breadth, 4 poles, equal to 22 or 25 yards.

Wiktionary

1. n. obsolete A field.
2. n. A unit of surface area (symbol a. or ac.), originally as much as a yoke of oxen could plough in a day; later defined as an area 1 chain (22 yd) by 1 furlong (220 yd), or 4,840 square yards. Equivalent to about 4,046.86 square metres.
3. n. in the plural, informal A large amount (of area).

GNU Webster's 1913

1. n. obsolete Any field of arable or pasture land.
2. n. A piece of land, containing 160 square rods, or 4,840 square yards, or 43,560 square feet. This is the English statute acre. That of the United States is the same. The Scotch acre was about 1.26 of the English, and the Irish 1.62 of the English.

WordNet 3.0

1. n. a territory of western Brazil bordering on Bolivia and Peru
2. n. a town and port in northwestern Israel in the eastern Mediterranean
3. n. a unit of area (4840 square yards) used in English-speaking countries