1. 占优势;盛行
    If you say, for example, that silence reigns in a place or confusion reigns in a situation, you mean that the place is silent or the situation is confused.

    e.g. Confusion reigned about how the debate would end...
           在这一争论如何结束的问题上人们陷入了混乱。
    e.g. A relative calm reigned over the city.
           城市相对平静了一些。

2. (国王或女王)统治，治理
    When a king or queen reigns, he or she rules a country.

    e.g. ...Henry II, who reigned from 1154 to 1189.
           1154至1189年间在位的亨利二世
    e.g. ...Queen Victoria, Britain's longest reigning monarch.
           维多利亚女王，英国历史上统治时间最长的君主

3. 称王;支配;主宰
    If you say that a person reigns in a situation or area, you mean that they are very powerful or successful.

reign的解释

    e.g. Connors reigned as the world No. 1 for 159 consecutive weeks...
           康纳斯连续159周排名世界第一。
    e.g. Coco Chanel reigned over fashion for half a century.
           可可·香奈儿在半个世纪里一直主宰着时尚界。

4. 占首要位置;占主导地位
    Someone or something that reigns supreme is the most important or powerful element in a situation or period of time.

    e.g. The bicycle reigned supreme as Britain's most popular mode of transport...
           当时自行车是英国最流行的交通工具。
    e.g. Senator Sam Nunn reigns supreme over the Senate Armed Services Committee.
           萨姆·纳恩参议员主导着参议院军事委员会。

5. (尤指统治集团制造的)恐怖统治时期
    A reign of terror is a period during which there is a lot of violence and killing, especially by people who are in a position of power.

reign

    e.g. The commanders accused him of carrying out a reign of terror.
           指挥官们谴责他实行恐怖统治。