1. a person who competes against someone in a contest or competition
2. a person who questions or disputes something established

Examples

• The young boxer was a serious challenger for the heavyweight title.
• Three challengers entered the race for mayor.
• She emerged as the main challenger to the incumbent president.
• The challenger questioned the company’s environmental policies.
• He was seen as a challenger to traditional teaching methods.
• The chess challenger studied her opponent’s previous games.
• Political challengers often promise significant changes.