to stop doing something

This course is really tough - sometimes I feeling like packing it all in. 这门课程太难了——有时候我都想放弃算了。

said to rudely tell someone to stop doing something that is annoying you

Pack it in, Julie - I'm trying to read. 别闹了，朱莉！我想看书。

to end your relationship with someone, or to stop meeting or spending time with them

"Is Emma still seeing Joe?" "No, she's packed him in." “埃玛还在和乔交往吗？”“没有，她已经和他断了。”

If an entertainment or exhibition packs people in, a large number of people come to see it.

Spielberg's new film is packing in the crowds. 斯皮尔伯格的新影片吸引了大批观众。

The latest computer exhibition is really packing them in. 最新的电脑展确实吸引了他们。

to manage to include a large number of things, activities, or people

We were only there four days but we packed a lot in. 我们在那儿只呆了4天时间，但我们设法安排了很多活动。