To move up is to move your body a little to make space for someone else to sit down or stand. (British and Australian English)
Examples of use:
1. Move up so this elderly lady can sit down as well.
2. Can you move up so that I can sit down, please?
3. The train was so crowded this morning. Even when we all moved up as much as we could, there was only room for one more passenger.
infinitive – move up
present simple – move up and moves up
-ing form – moving up
past simple – moved up
past participle – moved up
Image by Dale Ellerm