[dragonwriter]

It means that there is no defined limit (and thus, no accruing, and nothing to pay out if unused when you leave) of vacation hours. You still have to get your assigned work done.

What that means in practice will depend on the particular environment. It can mean that you have less stress over managing leave balances, it can mean that, because of workload, you can in practice neither take vacation nor be later compensated for not being able to take it.