Final answer:
In the Bible, a "mystery" refers to something that was once hidden but is now revealed in the person and work of Christ.
Step-by-step explanation:
In the Bible, a "mystery" is something that was once hidden to the people of the Old Testament and prophets but is now revealed in the person and work of Christ. The term "mystery" is used to describe the hidden truths and plans of God that were previously unknown but are now made known through Jesus. This concept is found in the New Testament, particularly in the writings of the apostle Paul.