As used in this chapter: “Association” means the joint underwriting association established pursuant to the provisions of this chapter. “Commercial liability insurance” means the commercial classes of insurance defined in §§ 38.2-117 and 38.2-118, but for the purposes of this chapter, does not include medical malpractice insurance as defined in § 38.2-2800, nuclear liability or any risks, lines, or subclassifications that are determined by the Commission to be uninsurable; provided, no such determination shall be based solely upon evidence that no insurers are then insuring such risk, line, or subclassification. The Commission may exclude from this definition any other line, subclassification or type of commercial liability insurance as it deems appropriate. “Incidental coverage” means any other type of liability insurance covering activities directly related to the continued and efficient delivery of business and professional services that: (i) cannot be separately obtained in the voluntary market because commercial liability insurance is being provided pursuant this chapter; and (ii) cannot be separately obtained through other involuntary market mechanisms. “Market assistance plan” means a voluntary association of insurers and insurance agents licensed to do business in the Commonwealth that is formed, pursuant to a plan of operation filed with and approved by the Commission, to assist with the individual placement of commercial liability insurance coverage that is not reasonably available on the voluntary market. “Net direct premiums written” means gross direct premiums written in this Commonwealth on all policies of liability insurance less (i) all return premiums on the policy, (ii) dividends paid or credited to policyholders, and (iii) the unused or unabsorbed portions of premium deposits on liability insurance. For the purposes of this chapter, “liability insurance” means the classes of insurance defined in §§ 38.2-117 through 38.2-119, and the liability portions of the insurance defined in §§ 38.2-124, 38.2-125 and 38.2-130 through 38.2-132.