adjective (a)

• located, suited for, or taking place in the open air(adj.all)

  Example:
  Outdoor clothes.
  Badminton and other outdoor games.
  A beautiful outdoor setting for the wedding.
  

  Synonym:
  out-of-door, outside
  Antonym:
  indoor
  

  source: wordnet30
• pertaining to or concerning the outdoors or outdoor activities(adj.pert)

  Example:
  Outdoor education is the area of teacher training concerned with training for outdoor activities.
  

  source: wordnet30
• Being, or done, in the open air; being or done outside of certain buildings, as poorhouses, hospitals, etc.; as, outdoor exercise; outdoor relief; outdoor patients.(adjective)

  source: webster1913