The Collaborative International Dictionary of English v.0.48:

Asylum \A*sy"lum\, n.; pl. E. Asylums, L. Asyla. [L. asylum,
   Gr. ?, fr. ? exempt from spoliation, inviolable; 'a priv. + ?
   right of seizure.]
   1. A sanctuary or place of refuge and protection, where
      criminals and debtors found shelter, and from which they
      could not be forcibly taken without sacrilege.
      [1913 Webster]

            So sacred was the church to some, that it had the
            right of an asylum or sanctuary.      --Ayliffe.
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   Note: The name was anciently given to temples, altars,
         statues of the gods, and the like. In later times
         Christian churches were regarded as asylums in the same
         sense.
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   2. Any place of retreat and security.
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            Earth has no other asylum for them than its own cold
            bosom.                                --Southey.
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   3. An institution for the protection or relief of some class
      of destitute, unfortunate, or afflicted persons; as, an
      asylum for the aged, for the blind, or for the insane; a
      lunatic asylum; an orphan asylum.
      [1913 Webster]

WordNet (r) 3.0 (2006):

asylum
    n 1: a shelter from danger or hardship [syn: refuge,
         sanctuary, asylum]
    2: a hospital for mentally incompetent or unbalanced person
       [syn: mental hospital, psychiatric hospital, mental
       institution, institution, mental home, insane asylum,
       asylum]