The word holocaust is not found in most versions of the Bible, but when it is used, it refers to a burnt offering, specifically a sacrificial offering that is entirely burned up in fire. This was prescribed by Moses, as handed down by God.
In modern usage, the Holocaust was the mass genocide of European Jews by the Nazis during World War II.
In general, holocaust refers to any wide-scale loss of life or a massive slaughter.
A lifelong student of the Bible, Peter DeHaan, PhD, wrote the 700-page website ABibleADay.com to encourage people to explore the Bible. His main blog and many books urge Christians to push past the status quo and reconsider how they practice their faith in every area of their lives.