Source : Webster's Revised Unabridged Dictionary (1913)

Workhouse \Work"house`\, n.; pl. {Workhouses}. [AS. weorch?s.]
   1. A house where any manufacture is carried on; a workshop.

   2. A house in which idle and vicious persons are confined to
      labor.

   3. A house where the town poor are maintained at public
      expense, and provided with labor; a poorhouse.

Source : WordNet®

workhouse
     n 1: a poorhouse where able-bodied poor are compelled to labor
     2: a county jail that holds prisoners for periods up to 18
        months