From WordNet (r) 3.0 (2006) [wn]:
outhouse
n 1: a small outbuilding with a bench having holes through which
a user can defecate [syn: outhouse, privy, {earth-
closet}, jakes]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
outhouse \out"house`\, n.
1. A small house or building at a little distance from the
main house; an outbuilding.
[1913 Webster]
2. Especially: A small building with one or more seats and a
pit underneath, intended for use as a toilet; a privy.
[PJC]