This means 挤进 (to force a lot of things into a small space)

• Eight children were crammed into the back of the car.
  八个孩子被塞进汽车的后座。
• The room was packed and we were crammed against the door.
  房间里挤满了人，我们挤在门口。

This also means 短时间内做很多事 (to do many things in a short period of time)

I had to cram three countries into a week’s business trip.
我不得不在一周的商务旅行中安排三个国家。

This also means 考前突击学习 (to try to learn a lot very quickly before an exam).

She’s cramming for her history exam.
她正在临时抱佛脚准备历史考试。