A more thorough explanation:

Definition: A lord who holds a title without owning a manor.

Example: In medieval England, a lord in gross was a nobleman who held a title such as Duke or Earl, but did not have a manor or estate to go with it.

Explanation: This means that the lord in gross did not have any land or property that came with their title. They were still considered to be of high rank and had certain privileges, but they did not have the same responsibilities or power as a lord who owned a manor. For example, they would not have had any tenants or serfs to work the land for them.