Jump Z-Tranche 

A Z-tranche that may start receiving principal payments before prior tranches are retired if market forces create a "triggering" event, such as a drop in Treasury yields to a defined level, or a prepayment experience that differs from assumptions by a specific margin. "Sticky" jump Z-tranches maintain their changed payment priority until they are retired. "Non sticky" jump Z-tranches maintain their priority only temporarily, for as long as the triggering event is present. Although jump Z-tranches are no longer issued, some still trade in the secondary market.