The Collaborative International Dictionary of English v.0.48:

Peristyle \Per"i*style\, n. [L. peristylum, Gr. peri`stylon,
   peri`stylos; peri` about + sty^los a column: cf. F.
   p['e]ristyle.] (Arch.)
   A range of columns with their entablature, etc.;
   specifically, a complete system of columns, whether on all
   sides of a court, or surrounding a building, such as the
   cella of a temple. Used in the former sense, it gives name to
   the larger and inner court of a Roman dwelling, the
   peristyle. See Colonnade.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Colonnade \Col`on*nade"\, n. [F. colonnade, It. colonnata, fr.
   colonna column. See Colonel.] (Arch.)
   A series or range of columns placed at regular intervals with
   all the adjuncts, as entablature, stylobate, roof, etc.
   [1913 Webster]

   Note: When in front of a building, it is called a portico;
         when surrounding a building or an open court or square,
         a peristyle.
         [1913 Webster]

WordNet (r) 3.0 (2006):

peristyle
    n 1: a colonnade surrounding a building or enclosing a court