The Collaborative International Dictionary of English v.0.48:

Venture \Ven"ture\, v. t.
   1. To expose to hazard; to risk; to hazard; as, to venture
      one's person in a balloon.
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            I am afraid; and yet I'll venture it. --Shak.
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   2. To put or send on a venture or chance; as, to venture a
      horse to the West Indies.
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   3. To confide in; to rely on; to trust. [R.]
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            A man would be well enough pleased to buy silks of
            one whom he would not venture to feel his pulse.
                                                  --Addison.
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The Collaborative International Dictionary of English v.0.48:

Venture \Ven"ture\, v. i. [imp. & p. p. Ventured; p. pr. & vb.
   n. Venturing.]
   1. To hazard one's self; to have the courage or presumption
      to do, undertake, or say something; to dare. --Bunyan.
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   2. To make a venture; to run a hazard or risk; to take the
      chances.
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            Who freights a ship to venture on the seas. --J.
                                                  Dryden, Jr.
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   To venture at, or To venture on or To venture upon, to
      dare to engage in; to attempt without any certainty of
      success; as, it is rash to venture upon such a project.
      "When I venture at the comic style." --Waller.
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The Collaborative International Dictionary of English v.0.48:

Venture \Ven"ture\ (?; 135), n. [Aphetic form of OE. aventure.
   See Adventure.]
   1. An undertaking of chance or danger; the risking of
      something upon an event which can not be foreseen with
      certainty; a hazard; a risk; a speculation.
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            I, in this venture, double gains pursue. --Dryden.
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   2. An event that is not, or can not be, foreseen; an
      accident; chance; hap; contingency; luck. --Bacon.
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   3. The thing put to hazard; a stake; a risk; especially,
      something sent to sea in trade.
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            My ventures are not in one bottom trusted. --Shak.
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   At a venture, at hazard; without seeing the end or mark;
      without foreseeing the issue; at random.
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            A certain man drew a bow at a venture. --1 Kings
                                                  xxii. 34.
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            A bargain at a venture made.          --Hudibras.
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   Note: The phrase at a venture was originally at aventure,
         that is, at adventure.
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WordNet (r) 3.0 (2006):

venture
    n 1: any venturesome undertaking especially one with an
         uncertain outcome
    2: an investment that is very risky but could yield great
       profits; "he knew the stock was a speculation when he bought
       it" [syn: speculation, venture]
    3: a commercial undertaking that risks a loss but promises a
       profit
    v 1: proceed somewhere despite the risk of possible dangers; "We
         ventured into the world of high-tech and bought a
         supercomputer" [syn: venture, embark]
    2: put forward, of a guess, in spite of possible refutation; "I
       am guessing that the price of real estate will rise again";
       "I cannot pretend to say that you are wrong" [syn: guess,
       venture, pretend, hazard]
    3: put at risk; "I will stake my good reputation for this" [syn:
       venture, hazard, adventure, stake, jeopardize]