The Collaborative International Dictionary of English v.0.48:

Quadrangle \Quad"ran`gle\, n. [F., fr. L. quadrangulum; quattuor
   four + angulus an angle. See Four, and Angle a corner.]
   [1913 Webster]
   1. (Geom.) A plane figure having four angles, and
      consequently four sides; any figure having four angles.
      [1913 Webster]

   2. A square or quadrangular space or inclosure, such a space
      or court surrounded by buildings, esp. such a court in a
      college or public school in England.
      [1913 Webster]

WordNet (r) 3.0 (2006):

quadrangle
    n 1: a four-sided polygon [syn: quadrilateral, quadrangle,
         tetragon]
    2: a rectangular area surrounded on all sides by buildings [syn:
       quad, quadrangle]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "quadrangle":
   Little Joe, arena, biquadrate, block, cincture, clos, close,
   confine, container, coop, court, courtyard, croft, curtilage,
   delimited field, enclave, enclosure, field, fold, forty, four,
   four-part diaphony, foursome, ground, kraal, list, lot, pale,
   paling, parcel of land, park, patch, pen, plat, plot,
   plot of ground, quad, quadrature, quadrennium, quadrilateral,
   quadrille, quadrinomial, quadruplet, quartet, quatern, quaternary,
   quaternion, quaternity, quatrefoil, real estate, rectangle,
   section, square, square dance, squaring, tetrad, tetragon,
   tetragram, tetragrammaton, tetrahedron, tetralogy, tetraphony,
   tetrapody, theater, toft, tract, yard