n.1. a. The act, business, or system of insuring.
b. The state of being insured.
c. A means of being insured.
2. a. An arrangement or agreement that protects someone from incurring future losses, as from damage, theft, illness, or death, especially a contract that transfers the risk of a specified loss to another party in exchange for the payment of a premium.
b. The sum or rate for which such a contract insures something.
c. The periodic premium paid for this coverage.
3. A protective measure: biking helmets that provide insurance against a head injury.