A managing general underwriter is actually the same as a managing general agent. The term is used in the health and life insurance fields. Their role is similar to that of a broker or agent, except they have the authority to underwrite policies.
Other duties of a managing general underwriter include pricing for policies, settling insurance claims and binding coverage. They can also be responsible for writing policies in smaller or remote locations where the insurance company does not want to spend the funds to set up an entire office, but still wants to have a local presence for potential insurance customers.