At the end of the day, I would not only be carrying a pile of shopping bags but also trying to squeeze in between other passengers on the train.

squeeze 是动词，意思是"挤、压"，指在有限的空间里用力移动或占据位置。 in 是介词，表示"进入...之间"或"在...内部"。 squeeze in 这个短语表示"挤进某个狭小空间"，通常指在拥挤的地方找到位置。