During the life of an application, items live and die. Before dying, they can become zombies.
Which means that the item still exists in the data description, that it can be used in the existing application code, but that the item must no longer be used when writing new code.
A zombie item takes space and therefore it should be deleted.
Zombie items are often found in the dead code.
In version 23, you have the ability to identify the zombie items in the analysis; they will be signaled when they are used.