Definition - What does HH Bond mean?
HH Bond is a non-marketable government security that pays semi-annual interest. Series HH bonds are issued with a $500 minimum value and may only be purchased by trading matured series EE bonds; they may not be purchased with cash.
Testopedia explains HH Bond
The US Treasury issues both negotiable and non-negotiable debt. Negotiable bonds can be traded eg: T-bills, T-notes, T-bonds. Savings bonds are non-negotiable, i.e.: they can not be traded. Savings bonds are purchased from a bank and redeemed, several years later, at a bank. EE savings bonds are sold at a discount and do not pay interest. An investor can roll their EE bonds into HH bonds which do pay semi-annual interest.