The Collaborative International Dictionary of English v.0.48:

Placard \Pla*card"\, v. t. [imp. & p. p. Placarded; p. pr. &
   vb. n. Placarding.]
   1. To post placards upon or within; as, to placard a wall, to
      placard the city.
      [1913 Webster]

   2. To announce by placards; as, to placard a sale.
      [1913 Webster]