1. CDO. An investment-grade security backed by a pool of various other securities. CDOs can be made up of any type of debt, in the form of bonds or loans, and usually do not deal with mortgages. CDOs, like CBOs and CMOs, are divided into slices, each slice is made up of debt which has a unique amount of risk associated with it. CDOs are often sold to investors who want exposure to the income generated by the debt but do not want to purchase the debt itself. 2. A general term used to refer to collateralized bond obligations (CBO), collateralized loan obligations (CLO), and collateralized mortgage obligations (CMO).