The Collaborative International Dictionary of English v.0.48:

Bailey \Bai"ley\, n. [The same word as bail line of palisades;
   cf. LL. ballium bailey, OF. bail, baille, a palisade,
   baillier to inclose, shut.]
   1. The outer wall of a feudal castle. [Obs.]
      [1913 Webster]

   2. The space immediately within the outer wall of a castle or
      fortress. [Obs.]
      [1913 Webster]

   3. A prison or court of justice; -- used in certain proper
      names; as, the Old Bailey in London; the New Bailey in
      Manchester. [Eng.] --Oxf. Gloss.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Bailey
    n 1: United States singer (1918-1990) [syn: Bailey, Pearl
         Bailey, Pearl Mae Bailey]
    2: English lexicographer who was the first to treat etymology
       consistently; his work was used as a reference by Samuel
       Johnson (died in 1742) [syn: Bailey, Nathan Bailey,
       Nathaniel Bailey]
    3: the outer courtyard of a castle
    4: the outer defensive wall that surrounds the outer courtyard
       of a castle