monoline
n.— «Only 13 companies belong to MICA. They are the closely regulated “monoline” mortgage insurance firms that only guarantee mortgage loans, with state laws forbidding them to enter any other insurance business.» —“Escrow Losses Could Hamper Private Issuers” by David LaGesse in New York City American Banker Feb. 13, 1985. (source: Double-Tongued Dictionary)