A more thorough explanation:

Term: Atavus
Definition: In Roman and civil law, an atavus is a male ancestor who is four generations removed from a person. This means that an atavus is the great-grandfather of a great-grandfather or great-grandmother. Example: If your great-grandfather had a great-grandfather, that person would be your atavus. This definition explains that an atavus is a specific type of ancestor in Roman and civil law. The example helps to illustrate how an atavus fits into a person's family tree.