1. 领袖；领导者
    The leader of a group of people or an organization is the person who is in control of it or in charge of it.

leader的反义词

    e.g. We now need a new leader of the party and a new style of leadership...
           我们现在需要一位新的政党领袖和一种新的领导作风。
    e.g. We are going to hold a rally next month to elect a new leader.
           我们打算下月举行集会，选举一位新的领导人。

2. （比赛或竞赛中的）领先者，占先者
    The leader at a particular point in a race or competition is the person who is winning at that point.

leader在线翻译

    e.g. The leaders came in two minutes clear of the field...
           优胜者较其他参赛者快两分钟。
    e.g. The world drivers' championship leader crossed the line ahead of the Swede.
           在世界车手锦标赛上，领先选手比瑞典人快一步冲线。

3. （产品或公司中的）首屈一指者，佼佼者
    The leader among a range of products or companies is the one that is most successful.

    e.g. Procter & Gamble is the leader in the mass market cosmetics industry.
           宝洁是大众化妆品行业中的领头羊。

4. （交响乐团的）首席小提琴手
    The leader of an orchestra is the most senior violin player, who acts as a deputy to the conductor.

5. （交响乐团的）指挥
    The leader of an orchestra is the conductor.

6. （报纸上的）社评，社论
    A leader in a newspaper is a piece of writing which gives the editor's opinion on an important news item.

7. （报纸的）要闻，头条
    A leader in a newspaper is the most important story in it.