A more thorough explanation:

Definition: The final sickness that leads to a person's death. It is also known as the last sickness.

Example: John's last illness was a severe case of pneumonia that he contracted during the winter. Despite receiving medical attention, his condition worsened, and he eventually passed away.

Explanation: The example illustrates how the term "last illness" refers to the final sickness that a person experiences before their death. In this case, John's pneumonia was the illness that led to his passing.