refers to the second, or sometimes the third, still in the process of distillation.
The final distillation still, for low wines from the wash still
Pot Still used for the second distillation and in which the low wines are transformed into Spirit.
The 2nd still used in the process. The low wines from the wash still are redistilled here to produce the foreshots, the heart of the run and the feints.
In pot still distillation, the second (occasionally third) still of the process.