The Collaborative International Dictionary of English v.0.48:
Open-air \O"pen-air`\, a. Taking place in the open air; outdoor; as, an open-air game or meeting. [1913 Webster]WordNet (r) 3.0 (2006):
open-air adj 1: in the open air; "an alfresco lunch"; "an open-air theater" [syn: alfresco, open-air(a)]