The Collaborative International Dictionary of English v.0.48:

Premise \Prem"ise\, n.; pl. Premises. [Written also, less
   properly, premiss.] [F. pr['e]misse, fr. L. praemissus, p.
   p. of praemittere to send before; prae before + mittere to
   send. See Mission.]
   1. A proposition antecedently supposed or proved; something
      previously stated or assumed as the basis of further
      argument; a condition; a supposition.
      [1913 Webster]

            The premises observed,
            Thy will by my performance shall be served. --Shak.
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   2. (Logic) Either of the first two propositions of a
      syllogism, from which the conclusion is drawn.
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   Note: "All sinners deserve punishment: A B is a sinner."
         [1913 Webster] These propositions, which are the
         premises, being true or admitted, the conclusion
         follows, that A B deserves punishment.
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               While the premises stand firm, it is impossible
               to shake the conclusion.           --Dr. H. More.
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   3. pl. (Law) Matters previously stated or set forth; esp.,
      that part in the beginning of a deed, the office of which
      is to express the grantor and grantee, and the land or
      thing granted or conveyed, and all that precedes the
      habendum; the thing demised or granted.
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   4. pl. A piece of real estate; a building and its adjuncts;
      as, to lease premises; to trespass on another's premises.
      [1913 Webster]

WordNet (r) 3.0 (2006):

premises
    n 1: land and the buildings on it; "bread is baked on the
         premises"; "the were evicted from the premises"