1. 
[syn: outdoors, out-of-doors, open air, open]
WordNet (r) 3.0 (2006):
open air
    n 1: where the air is unconfined; "he wanted to get outdoors a
         little"; "the concert was held in the open air"; "camping
         in the open" [syn: outdoors, out-of-doors, open air,
         open]
Moby Thesaurus II by Grady Ward, 1.0:
22 Moby Thesaurus words for "open air":
   aerial, aeriform, aery, airish, airlike, airy, alfresco,
   atmospheric, breezy, ethereal, exposed, light, open, out,
   out-of-door, out-of-doors, outdoor, outside, pneumatic, roomy,
   tropospheric, without