The word "prior" has several meanings, depending on its context.
1) In chronological order or sequence; before in time. For example, "I completed my work prior to leaving for the day."
2) Of higher rank or importance. For example, "He was given priority as he had been with the company longer than others."
3) Belonging to an earlier period of time; ancient. For example, "The ruins of the old castle date back to a prior era."
4) Denoting a monk belonging to a religious order. For example, "He entered the monastery as a novice and later became a fully professed member or 'prior'."