The Collaborative International Dictionary of English v.0.48:

Open \O"pen\ v. t. [imp. & p. p. Opened; p. pr. & vb. n.
   Opening.] [AS. openian. See Open,a.]
   1. To make or set open; to render free of access; to unclose;
      to unbar; to unlock; to remove any fastening or covering
      from; as, to open a door; to open a box; to open a room;
      to open a letter.
      [1913 Webster]

            And all the windows of my heart
            I open to the day.                    --Whittier.
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   2. To spread; to expand; as, to open the hand.
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   3. To disclose; to reveal; to interpret; to explain.
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            The king opened himself to some of his council, that
            he was sorry for the earl's death.    --Bacon.
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            Unto thee have I opened my cause.     --Jer. xx. 12.
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            While he opened to us the Scriptures. --Luke xxiv.
                                                  32.
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   4. To make known; to discover; also, to render available or
      accessible for settlements, trade, etc.
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            The English did adventure far for to open the North
            parts of America.                     --Abp. Abbot.
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   5. To enter upon; to begin; as, to open a discussion; to open
      fire upon an enemy; to open trade, or correspondence; to
      open an investigation; to open a case in court, or a
      meeting.
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   6. To loosen or make less compact; as, to open matted cotton
      by separating the fibers.
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   To open one's mouth, to speak.

   To open up, to lay open; to discover; to disclose.
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            Poetry that had opened up so many delightful views
            into the character and condition of our "bold
            peasantry, their country's pride."    --Prof.
                                                  Wilson.
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The Collaborative International Dictionary of English v.0.48:

opened \opened\ adj.
   1. having the covering skin pulled back; -- used of mouth or
      eyes; as, his mouth slightly opened. Opposite of closed.
      [Narrower terms: agape(predicate), gaping, yawning ;
      {agaze, staring ; {round-eyed, wide ]

   Syn: open.
        [WordNet 1.5]

   2. having the seal broken so as to reveal the contents; as,
      the letter was already opened.

   Syn: open.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

opened
    adj 1: used of mouth or eyes; "keep your eyes open"; "his mouth
           slightly opened" [syn: {open, opened] [ant: closed,
           shut]
    2: made open or clear; "the newly opened road"
    3: not sealed or having been unsealed; "the letter was already
       open"; "the opened package lay on the table" [syn: open,
       opened]