It can be a very sensual spot to touch lightly as a form of flirting, or just to move past people.
I came across this sentence from here. "Move past" seems to be a slang, and I haven't managed to find it in dictionaries. What's it supposed to mean here?
No slang here. 'Move' and 'past' have their ordinary dictionary meanings. Imagine that you want to move along a narrow space in which someone is standing, and you will pass by their back. As you pass them (move past them) you might lightly place your hand on their back to let them know that you are there (it might be noisy and they might step back). Also you could be trying to move through a crowd of people pressed close together, and the touch will indicate that you want to move past them.
Imagine you are walking on a narrow path and someone is walking slowly in front of you. You might want to overtake him, and to do so you gently touch him on his back to get his attention so that he will make way for you. Move past literally means the combination of the two words, to be from a position behind him to a position in front of him, in this example.
