There are many synonyms that can be used to describe an ancient Roman soldier. One of the most commonly used terms is "legionary," which refers to a member of a legion, the basic unit of the Roman army. Other synonyms include "centurion," which refers to a soldier in charge of a century, a group of around 80 soldiers, and "praetorian," which refers to a member of the Praetorian Guard, a group of elite soldiers responsible for protecting the Roman emperor. Additional synonyms for an ancient Roman soldier might include "miles," "infantryman," or simply "Roman warrior." Whatever term you choose to use, it is clear that these soldiers played a vital role in the history of ancient Rome.