what does blacklist mean?
If you're referring to Verizon's blacklist, A phone would normally have been lost / stolen / account closed prior to completion of contract.
Effectively not letting the phone get on Verizon proper or any Verizon MVNO's.
It's basically a paperweight (or an MP3 player / voip phone) for at least 6 months or more.
Eventually things come off the blacklist (everything that I've ever run into has (running an independent cell store) but your mileage may vary).