A more thorough explanation:

Definition: Mesne (pronounced as “meen;” but also “meien” and “mean”) is a legal term that means intermediate or intervening. It refers to the middle point between two extremes. In feudal law, it was used to describe a person or interest that was subordinate to one person's role or interest but superior to another's.

For example, a mesne lord is a landlord who has tenants holding under him, while himself was answerable to a superior lord. Mesne process is a writ issued in the course of a lawsuit between the beginning and end of the process. Mesne profits are profits derived from land while in wrongful possession.

Today, the term is seldom used except for the phrase “mesne profits.” Mesne profits refer to profits derived from land while in wrongful possession. For instance, if someone occupies a piece of land without the owner's permission and makes a profit from it, they may be required to pay mesne profits to the rightful owner.