A more thorough explanation:

Definition: Usurpation is the act of taking someone else's position, office, or authority without permission or legal right.

For example, if someone takes over a company without the owner's permission, that is an act of usurpation. Another example is when a person claims to have the authority to make decisions for a group or organization, even though they were not elected or appointed to that position.

Usurpation can also happen in the context of advowson, which is the right to nominate a person to a vacant benefice in the church. If someone presents a clerk to a church without the right to do so, that is an act of usurpation of advowson.