IBF is the short name of one of the big groups that run professional boxing — boxing for money, with title belts. The letters stand for International Boxing Federation. If a boxer holds an IBF title, people call that person a world champion at that weight. Though actually, boxing does not have only one “the” world champion. There are several of these groups (you will also hear WBC, WBA, and WBO), and each can give its own belt. So an IBF champion is a real world champion — just not always the only person on earth with a belt in that weight. You see IBF on sports news and fight posters. Fans say the three letters; almost nobody says the full name. It is insider sports language, not school language. The same three letters can stand for other groups in other fields, but if the story is about boxing, IBF means this one.