1. （大）体积；（大）量
    You can refer to something's bulk when you want to emphasize that it is very large.

    e.g. The truck pulled out of the lot, its bulk unnerving against the dawn.
           卡车从空地上开出来，庞大的车身小心翼翼地避让着草坪。
    e.g. ...the shadowy bulk of an ancient barn.
           一座古老谷仓的巨大阴影

2. 庞大的身躯；巨大的体重；肥硕的体形
    You can refer to a large person's body or to their weight or size as their bulk .

bulk的反义词

    e.g. Bannol lowered his bulk carefully into the chair...
           班诺尔小心翼翼地将肥硕的身躯落座到椅子上。
    e.g. Despite his bulk he moved lightly on his feet.
           尽管他身形庞大，移动起来还是很灵巧。

3. 主体；大部分
    The bulk of something is most of it.

    e.g. The bulk of the text is essentially a review of these original documents...
           文章的主要部分基本是对这些原始文件的回顾。
    e.g. The vast bulk of imports and exports are carried by sea.
           大部分的进出口货物都是通过海路运输的。

4. 大宗，大批（买卖）
    If you buy or sell something in bulk, you buy or sell it in large quantities.

    e.g. Buying in bulk is more economical than shopping for small quantities.
           批量采购要比零买实惠很多。
    e.g. ...bulk purchasing.
           大宗采购

相关词组：bulk up