Final answer:
The second oldest wine level in a solera system is called the first criadera, which is a level used in the aging process of sherry, where younger wine is used to replenish older wine drawn for bottling.
Step-by-step explanation:
The term for the second oldest wine level in a solera system is called the first criadera or first nursery. The solera system is a method used primarily for aging sherry and involves stacking barrels of wine by age. The oldest barrels sit at the bottom (the solera), and the youngest at the top.
As wine is drawn off from the oldest barrels for bottling, it is replenished with wine from the next oldest level, and so on, with the barrels at the very top filled with the youngest wine. Therefore, the second oldest wine level is directly above the solera, known as the first criadera.