If you cram things or people into a container or place, you put them into it, although there is hardly enough room for them.

If people cram into a place or vehicle or cram a place or vehicle, so many of them enter it at one time that it is completely full.

If you cram a hat on, you put it on, especially in a hurry.

If you are cramming for an examination, you are learning as much as possible in a short time just before you take the examination.