What is Assumption Of Risk?

Legal Definition
Assumption of risk is a defense in the law of torts, which bars or reduces a plaintiff's right to recovery against a negligent tortfeasor if the defendant can demonstrate that the plaintiff voluntarily and knowingly assumed the risks at issue inherent to the dangerous activity in which he was participating at the time of his or her injury.

What is usually meant by assumption of risk is more precisely termed primary or "express" assumption of risk. It occurs when the plaintiff has either expressly or implicitly relieved the defendant of the duty to mitigate or relieve the risk causing the injury from which the cause of action arises. It operates as a complete bar to liability on the theory that upon assumption of the risk, there is no longer a duty of care running from the defendant to the plaintiff; without a duty owed by the defendant, there can be no negligence on his part. However, primary assumption of risk is not a blanket exemption from liability for the operators of a dangerous activity. The specific risk causing the injury must have been known to, and appreciated by, the plaintiff in order for primary assumption of risk to apply. Also, assumption of risk does not absolve a defendant of liability for reckless conduct.

This defense is commonly asserted in cases of injuries occurring during risky recreational activities, such as skiing, paragliding, and scuba diving, but actually extends to all dangerous activities. Thus, for example, it was held that a visitor to the Burning Man festival assumed the risk of getting burned.

Secondary assumption of risk is a rather different doctrine akin in some respects to comparative negligence. The difference was explained by the Supreme Court of California as follows:

In cases involving ‘primary assumption of risk’—where, by virtue of the nature of the activity and the parties' relationship to the activity, the defendant owes no legal duty to protect the plaintiff from the particular risk of harm that caused the injury—the doctrine continues to operate as a complete bar to the plaintiff's recovery. In cases involving ‘secondary assumption of risk’—where the defendant does owe a duty of care to the plaintiff, but the plaintiff proceeds to encounter a known risk imposed by the defendant's breach of duty—the doctrine is merged into the comparative fault scheme, and the trier of fact, in apportioning the loss resulting from the injury, may consider the relative responsibility of the parties.
-- Wikipedia
Legal Definition
Potential plaintiffs sometimes take the risk of injury onto themselves and absolve potential defendants from any liability. Formerly, this was an affirmative defense available to defendants, but has since been subsumed by contributory and comparative negligence in most jurisdictions. see, e.g. Justice Ginsburg's dissent in Honda Motor Co. v. Oberg, 512 US 415 (1994).
Legal Definition
A term or condition in a contract of employment, either express or implied from the circumstances of the employment, by which the employe agrees that dangers of injury ordinarily or obviously incident to the discharge of his duty in the particular employment shall be at his own risk. Narramore v. Railway Co., 96 Fed, 301, 37 C. C. A. 499, 48 L. R. A. 68; Faulkner v. Mining Co., 23 Utah, 437, 66 Pac. 799; Railroad Co. v. Touney, 67 Ark. 209, 54 S. W. 577, 77 Am. St. Rep. 109; Bodie v. Railway Co., 61 S. C. 468, 39 S. El 715; Martin v. Railroad Co., 118 Iowa, 148, 91 N. W. 1034, 59 In R. A. 698, 96 Am. St. Rep. 371.
-- Black's Law Dictionary
Legal Definition
A term of the contract of employment, expressed or implied from the circumstances of the employment, by which the servant agrees that dangers of injury obviously incident to the discharge of his duty shall be at his risk. See 48 L. R. A. 68.
-- Ballentine's Law Dictionary