A more thorough explanation:

PROSOCERUS

Prosocerus is a Latin term used in civil law to refer to a person's grandmother-in-law, either on the wife's or husband's side.

For instance, if John is married to Mary, and Mary's grandmother is still alive, then Mary's grandmother is John's prosocerus. Similarly, if Jane is married to Tom, and Tom's grandmother is still alive, then Tom's grandmother is Jane's prosocerus.

Another example could be if Sarah is married to David, and David's grandmother is deceased, then David's mother's mother would be Sarah's prosocerus.

The term prosocerus is used to describe the relationship between a person and their spouse's grandmother. The examples illustrate how the term is used in different scenarios, depending on the marital relationship and the status of the grandmother. It is important to note that the term is not commonly used in modern times and is mostly found in legal documents or historical texts.