What does the word acre mean?

Usage examples for acre

  1. The poor land groans with its birth- pains, and brings forth scarcely a hundred pounds of cotton to the acre, where fifty years ago it yielded eight times as much. – The Souls of Black Folk by W. E. B. Du Bois
  2. There was an orchard either side of the lane which led from the highway, and, in the rear of the house, an acre of ground, which had been cultivated at some time in the past. – The Princess and Joe Potter by James Otis