Redemption of a debt security due to unusual circumstances. For example, some bond issues can be redeemed prior to the scheduled maturity because of the destruction of the facility that was financed by the bonds. Extraordinary calls are most frequently used to retire single-family mortgage revenue bonds when homeowners refinance their mortgages. Extraordinary calls, generally made at par, nearly always work to the disadvantage of bondholders. Also called extraordinary redemption, special call. See also optional call.