The Collaborative International Dictionary of English v.0.48:

Placitum \Plac"i*tum\, n.; pl. Placita. [LL. See Placit.]
   1. A public court or assembly in the Middle Ages, over which
      the sovereign president when a consultation was held upon
      affairs of state. --Brande & C.
      [1913 Webster]

   2. (Old Eng. Law) A court, or cause in court.
      [1913 Webster]

   3. (Law) A plea; a pleading; a judicial proceeding; a suit.
      --Burrill.
      [1913 Webster]