It is a bond that does not give periodic interest payments. In spite of that, interest is added to the principal balance of the bond and is either paid at maturity or, at some point, the bond starts to pay both principal and interest on the basis of the accrued principal and interest to that point.
When the bond starts to pay principal and interest on the basis of accrued principal and interest at that point then this is called as a Z tranche and is ordinary in collateralized mortgage obligations (CMOs). In a CMO that involves a Z tranche, the interest payments that else would be paid to the Z-tranche holder are utilized to pay down the principal of the other tranche. After that tranche is paid off, the Z tranche starts to pay down based on the original principal of the tranche added with the accrued interest. Parallel to a zero-coupon bond, an accrual bond or Z tranche has partial or no reinvestment risk. Though, accrual bonds, by definition, have a longer duration than bonds with the equal maturity that create regular interest or principal and interest payments. As such, accrual bonds are exposing to greater interest rate risk than bonds that make periodic payments over their full terms.