The Collaborative International Dictionary of English v.0.48:

Outbuild \Out*build"\, v. t. [imp. & p. p. Outbuiltor
   Outbuilded; p. pr. & vb. n. Outbuilding.]
   To exceed in building, or in durability of building.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Outbuilding \Out"build`ing\, n.
   A building separate from, and subordinate to, the main house;
   an outhouse.
   [1913 Webster]

WordNet (r) 3.0 (2006):

outbuilding
    n 1: a building that is subordinate to and separate from a main
         building

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "outbuilding":
   Nissen hut, Quonset hut, booth, crib, gatehouse, hut, hutch, kiosk,
   lean-to, outhouse, pavilion, sentry box, shack, shanty, shed,
   stall, tollbooth, tollhouse