The debt or series of debts, collectively, represented by a series of debentures; a debt secured by a trust deed of property for the benefit of the holders of shares in the debt or of a series of debentures. By the terms of much debenture stock the holders are not entitled to demand payment until the winding up of the company or default in payment; in the winding up of the company or default in payment; in the case of railway debentures, they cannot demand payment of the principal, and the debtor company cannot redeem the stock, except by authority of an act of Parliament.