The Collaborative International Dictionary of English v.0.48:

Battering-ram \Bat"ter*ing-ram`\, n.
   1. (Mil.) An engine used in ancient times to beat down the
      walls of besieged places.
      [1913 Webster]

   Note: It was a large beam, with a head of iron, which was
         sometimes made to resemble the head of a ram. It was
         suspended by ropes to a beam supported by posts, and so
         balanced as to swing backward and forward, and was
         impelled by men against the wall. --Grose.
         [1913 Webster]

   2. A blacksmith's hammer, suspended, and worked horizontally.
      [1913 Webster]