A more thorough explanation:

Definition: Casatus (pronounced kuh-zay-tuhs) is a historical term used to describe a vassal or feudal tenant who owned a casata.

Example: In medieval Europe, a casatus was a person who held a casata, which was a small piece of land granted to them by a lord in exchange for their loyalty and service.

Explanation: The term casatus is derived from the Latin word "casata," which means "cottage" or "small house." A casatus was a person who owned a casata, which was typically a small plot of land with a simple dwelling on it. In feudal society, a casatus was a member of the lower nobility who owed allegiance to a lord in exchange for protection and the right to use the land. The example illustrates how the term was used in medieval Europe to describe a specific type of feudal tenant.