With respect to structured products with barrier mechanism, it is a coupon (interest payment) that is carried over to the next observation date if the product (e.g., note), at a given observation date, fails to meet the coupon payment requirements as defined in the structure. However, if payment requirements are met at a certain observation date, all coupons that have not previously been paid will snowball- become due for payment all together.

Simply put, the holder (investor) has a better change to obtain the expected return on the product, irrespective of market downturn over the lifespan of the structure provided that coupon payment requirements are met at a given point in time before expiration date. In which case, all coupons up to that point in time will snowball, becoming payable.

It is also referred to as a memory coupon.