"A dog at the doorstep" 或者 "A dog by the door" 是表示狗在门旁边的英语表达方式。这个短语的来源源于狗作为人类家庭的守卫者和伴侣，常常被训练在家门口巡逻。

例句：

There's a dog at the doorstep barking at everyone who walks by.
(有一只狗在门口对着每个走过的人大声吠叫。)
The dog by the door wagged its tail excitedly as its owner came home.
(当主人回家时，门旁边的狗兴奋地摇着尾巴。)