When you and the person you're dating decide you're going to move in together, and you decide to move into one persons existing apartment because they have more stuff than you, and it's so much easier for the person with less stuff to move in.
If a person with a lot of stuff moves in, it's a big deal, it's noisy, it can be a real hard move-in. But if the person with less stuff moves in to the place where all the stuff is already, it's not a huge ordeal, it's quiet, no one needs a u-haul, therefore it's a soft move-in.
All the benefits of living together with as little hardship of moving.
Girl: "I'd love to meet up with you tonight, but I've got to clear out some room upstairs for my boyfriends massive computer system and I'll make some bathroom space too."
Other girl: "Oh cool, you guys are doing a soft move-in, huh?"
Girl: "Yeah, I'm excited! He gets a closet too, but doesn't really have much other stuff."
When you make someone think you are pulling a dick move but you dont follow through.
Hah, the look on that ladies face when you faked pulling into her parkings spot, what a soft dick move!