1. (食物、产品或活动)主要的，基本的
    A staple food, product, or activity is one that is basic and important in people's everyday lives.

staple在线翻译

    e.g. Rice is the staple food of more than half the world's population...
           稻米是全世界一半以上人口的主食。
    e.g. The Chinese also eat a type of pasta as part of their staple diet...
           中国人也把一种面食作为他们的主食之一。

2. 主要部分;重要内容
    A staple is something that forms an important part of something else.

    e.g. Political reporting has become a staple of American journalism.
           政治新闻已成为美国新闻报道的主要内容。

3. 订书钉
    Staples are small pieces of bent wire that are used mainly for holding sheets of paper together firmly. You put the staples into the paper using a device called a stapler.

4. 用订书机订
    If you staple something, you fasten it to something else or fix it in place using staples.

    e.g. Staple some sheets of paper together into a book.
           用订书机将几页纸装订成册。
    e.g. ...polythene bags stapled to an illustrated card.
           订在一张插图卡片上的几个塑料袋