The Collaborative International Dictionary of English v.0.48:

Piazza \Pi*az"za\, n.; pl. Piazzas. [It., place, square,
   market place, L. platea street, courtyard. See Place.]
   An open square in a European town, especially an Italian
   town; hence (Arch.), an arcaded and roofed gallery; a
   portico. In the United States the word is popularly applied
   to a veranda.
   [1913 Webster]

         We walk by the obelisk, and meditate in piazzas. --Jer.
                                                  Taylor.
   [1913 Webster]