The Collaborative International Dictionary of English v.0.48:

Boudoir \Bou*doir"\, n. [F., fr. bouder to pout, be sulky.]
   A small room, esp. if pleasant, or elegantly furnished, to
   which a lady may retire to be alone, or to receive intimate
   friends; a lady's bedroom; a lady's (or sometimes a
   gentleman's) private room. --Cowper.
   [1913 Webster]

WordNet (r) 3.0 (2006):

boudoir
    n 1: a lady's bedroom or private sitting room