1. [n]  a venture undertaken without regard to possible loss or injury; "he saw the rewards but not the risks of crime"; "there was a danger he would do the wrong thing"
2. [n]  a source of danger; "drinking alcohol is a health hazard"
3. [v]  take a risk in the hope of a favorable outcome; "When you buy these stocks you are gambling"
4. [v]  expose to a chance of loss or damage; "We risked losing a lot of money in this venture"; "Why risk your life?"

Risk
A yacht in the middle of the Mediterranean Sea might seem like an ideal vacation to many, but for racehorse jockey Roland Britten it is nothing but a nightmare as this seemingly ideal location is where he awakes, tied and blindfolded, the day after winning a championship horse race.

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1. \Risk\, n. [F. risque; cf. It. risco, risico, rischio, Pg.
   risco, Sp. riesgo, and also Sp. risco a steep rock; all
   probably fr. L. resceare to cut off; pref. re- re- + secare
   to cut; -- the word having been probably first used among
   sailors. See {Section}.]
   1. Hazard; danger; peril; exposure to loss, injury, or
      destruction.
            The imminent and constant risk of assassination, a
            risk which has shaken very strong nerves.
                                                  --Macaulay.
   2. (Com.) Hazard of loss; liabillity to loss in property.
   {To run a risk}, to incur hazard; to encounter danger.
   Syn: Danger; hazard; peril; jeopardy; exposure. See {Danger}.
   

2. \Risk\, v. t. [imp. & p. p. {Risked}; p. pr. & vb. n.
   {Risking}.] [CF. F. risquer. See {Risk}, n.]
   1. To expose to risk, hazard, or peril; to venture; as, to
      risk goods on board of a ship; to risk one's person in
      battle; to risk one's fame by a publication.
   2. To incur the risk or danger of; as, to risk a battle.
   Syn: To hazard; peril; endanger; jeopard.