见惯了的人(或东西);存在已久故不为人注意的人(或事物)
a person or thing that you are so used to seeing that you no longer notice them
I worked there so long that I became part of the furniture.我在那里工作得太久,都不为人注意了。
释义来自《牛津高阶英汉双解词典》第 9 版