The Collaborative International Dictionary of English v.0.48:

Bocardo \Bo*car"do\, n. [A mnemonic word.]
   1. (Logic) A form of syllogism of which the first and third
      propositions are particular negatives, and the middle term
      a universal affirmative.
      [1913 Webster]

            Baroko and Bocardo have been stumbling blocks to the
            logicians.                            --Bowen.
      [1913 Webster]

   2. A prison; -- originally the name of the old north gate in
      Oxford, which was used as a prison. [Eng.] --Latimer.
      [1913 Webster]