The Collaborative International Dictionary of English v.0.48:

Bordel \Bor"del\, Bordello \Bor*del"lo\, n. [F. bordel, orig. a
   little hut, OF. borde hut, cabin, of German origin, and akin
   to E. board,n.See. Board, n.]
   A brothel; a bawdyhouse; a house devoted to prostitution.
   [Obs.] --B. Jonson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bordello \Bor"del*lo\, n.
   a building where prostitutes are available for hire; a
   brothel.

   Syn: whorehouse, whore house, brothel, bagnio, house of
        prostitution, house of ill repute, bawdyhouse, bawdy
        house, cathouse, sporting house.
        [PJC + WordNet 1.5]

WordNet (r) 3.0 (2006):

bordello
    n 1: a building where prostitutes are available [syn:
         whorehouse, brothel, bordello, bagnio, house of
         prostitution, house of ill repute, bawdyhouse,
         cathouse, sporting house]