REINSURANCE: A frequently used term in reinsurance referring to an incident, happening or event which triggers coverage under an occurrence-based reinsurance agreement. The definition of an occurrence will vary, depending upon the intent and interests of the parties and may not necessarily match the definition of occurrence in the original policy
***
US: An accident, including continuous or repeated exposure to substantially the same general, harmful conditions, that results in bodily injury or property damage during the period of an insurance policy.
***
REINSURANCE: An adverse contingent accident or event neither expected nor intended from the point of view of the insured. With regard to limits on occurrences, property catastrophe reinsurance agreements frequently define adverse vents having a common cause and sometimes within a specified time frame, for example 72 hours, as being one occurrence. This definition prevents multiple retentions and reinsurance limits from being exposed in a single catastrophe loss.
***
An incident that causes an insured loss. This is considered different than an accident, because an occurrence does not have to be sudden and unexpected. An occurrence can also be the result of repeated exposure to a certain condition, as long as it is not intentional or predicted by the insured.
***
UK: Generally an event that results in an insured loss. Specifically, an event that triggers a ‘losses-occurring’ liability policy that covers injury or damage occurring during the policy period even if the claim is brought after the policy has expired. The occurrence may be a single accident or, by policy definition, injuries to multiple victims due to exposure to the same harmful conditions on a continuing basis (claims series clause) or adverse events all occurring within a specified time (hours clause). Contrast with claims-made policies. See OCCURRENCE TRIGGER THEORIES; LIABILITY SEQUENCE.
***
In general, an event that triggers coverage under any policy generally unexpected and unintended. Specifically, an event that triggers coverage under an occurrence-based liability policy. Such a policy covers injury or damage that occurs during the policy period even if claim is brought months or even years after the policy has expired. See Claims-made for the alternate arrangement. Also see Accident. Often defined in policy language as an accident, including continuous or repeated exposure to the same general harmful conditions that result in bodily injury or property damage.
***
In Insurance contract language, continued or repeated exposure to conditions which unexpectedly results in injury during the period an Insurance Policy is in effect; in contrast to sudden injury or damage from an accident which takes place at a specific time and location. In some lines of business, such as liability an occurrence is distinguished from accident in that the loss doesn’t have to be sudden and fortuitous and can result from continuous or repeated exposure which results in bodily injury or property damage neither expected not intended by the insured.

A policy covering claims that arise out of damage or injury that took place during the policy period (or reinsurance contract period when used to describe reinsurance coverage) regardless of when claims are made. Most commercial general liability insurance is written on an occurrence form. Contrast with Claims-Made coverage.
***
Same as occurrence basis refers to a type of insurance coverage that insures occurrences taking place during the policy period, regardless when the claim arising out of the occurrence is first made. This coverage is in contrast to claims made coverage, which insures claims first made during the policy period, regardless when the alleged wrongdoing occurred.

A provision in most property per risk reinsurance contracts that limits the reinsurer’s liability for all risks involved in one occurrence. See Occurrence.