WordNet (r) 3.0 (2006):

gazebo
    n 1: a small roofed building affording shade and rest [syn:
         gazebo, summerhouse]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "gazebo":
   Texas tower, alcove, arbor, beacon, belvedere, bleachers, bower,
   bridge, conning tower, conservatory, gallery, garden, glasshouse,
   grandstand, greenhouse, kiosk, lathhouse, lighthouse, lookout,
   loophole, observation post, observatory, outlook, overlook, pagoda,
   peanut gallery, peephole, pergola, pharos, retreat, ringside,
   ringside seat, sighthole, summerhouse, top gallery, tower,
   watchtower