From The Collaborative International Dictionary of English v.0.48 :
Outdoors \Out"doors`\, adv.
Out of the house; out of doors; in the open air; abroad.
[1913 Webster +PJC]
From WordNet (r) 3.0 (2006) :
outdoors
adv 1: outside a building; "in summer we play outside" [syn:
outside, outdoors, out of doors, alfresco] [ant:
indoors, inside]
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]