Is the translation of a word (tse'med), which properly means a yoke, and denotes a space of ground that may be ploughed by a yoke of oxen in a day. It is about an acre of our measure (Isaiah 5:10; 1 Samuel 14:14).

Noah Webster's New International Dictionary of the English Language

(n.) A piece of land, containing 43,560 square feet or 1/640 of a square mile. 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.