Used to say that something happens before another event or time.
“Please submit all required documents prior to your start date.”
“Prior to the meeting, please review the attached report.”
Formal correspondence in Reading Part 1 frequently uses 'prior to' instead of 'before' to sound more official. When you see it, check what event comes right after it, since sequence-of-events questions are common in this task.
Synonyms: before, ahead of, in advance of