The Collaborative International Dictionary of English v.0.48:

Proposal \Pro*pos"al\, n. [From Propose.]
   1. That which is proposed, or propounded for consideration or
      acceptance; a scheme or design; terms or conditions
      proposed; offer; as, to make proposals for a treaty of
      peace; to offer proposals for erecting a building; to make
      proposals of marriage. "To put forth proposals for a
      book." --Macaulay.
      [1913 Webster]

   2. (Law) The offer by a party of what he has in view as to an
      intended business transaction, which, with acceptance,
      constitutes a contract.
      [1913 Webster]

   Syn: Proffer; tender; overture. See Proposition.
        [1913 Webster]

WordNet (r) 3.0 (2006):

proposal
    n 1: something proposed (such as a plan or assumption)
    2: an offer of marriage [syn: marriage proposal, proposal of
       marriage, marriage offer, proposal]
    3: the act of making a proposal; "they listened to her proposal"
       [syn: proposal, proposition]