Are these two verbs - to move over and to squash up - interchangeable? Do they mean the same?
- If you squash up/move over there'll be room for Tim on the sofa as well.
- Could you please squash up/move over? That's my son's seat.
Well, "move over" is simply a request for someone to move.
"Squish over" is asking someone to move in a way that makes room for you to sit by forcing the other people closer together.
Say you are seated on a couch, in the center. I sit on the right side and ask you to move over (to your left). This way we are both on the couch, but not seated next to each other. We both have extra room.
On the other hand, if you and a friend are both sitting comfortably on a couch, I might ask you to squish over so I can sit on the end. You would have to move closer to your friend, and maybe he moves over towards the other edge some to make room for you to move over. We are all now seated, but we have little extra room. We have squished together.
In the first case, I could not ask you to squish over, as there is no squishing involved. Lots of room.
In the second, I could ask you to move over, and the same movement would occur.
In summary, squishing always involves movement, but movement does not have to involve squishing.