The Collaborative International Dictionary of English v.0.48:

hideaway \hideaway\ n.
   a hiding place; usually a remote place used by outlaws.

   Syn: hideout, den.
        [WordNet 1.5]

   2. an area where one can be alone and undisturbed.

   Syn: retreat.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

hideaway
    n 1: a hiding place; usually a remote place used by outlaws
         [syn: hideout, hideaway, den]
    2: an area where you can be alone [syn: hideaway, retreat]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "hideaway":
   adytum, ashram, asylum, bolt-hole, cache, cell, cloister,
   concealment, corner, cover, covert, coverture, cranny, cubby,
   cubbyhole, dark corner, den, dugout, foxhole, funk hole, hermitage,
   hideout, hidey hole, hiding, hiding place, hole, holy of holies,
   ivory tower, lair, mew, niche, nook, privacy, recess, refuge,
   retreat, safe haven, sanctuary, sanctum, sanctum sanctorum,
   secret place, stash, undercovert