Definition of leader noun from the Oxford Advanced American Dictionary

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leader

noun
/ˈlidər/
 
 
1 a person who leads a group of people, especially the head of a country, an organization, etc.a political/spiritual, etc. leaderthe leader of the movementunion leadersHe was not a natural leader.She's a born leader.2 a person or thing that is the best, or in first place in a race, business, etc.She was among the leaders of the race from the start.The company is a world leader in electrical goods. see also market leader