Scratch And Dent. It means it's not perfect, but it's almost perfect.
Take a good hard look at this Neato Vacuum. Notice how it's designed for pet owners. Notice how it's robotic and as such will zip around independent of a human. Is that a thing you want to be perfect? Is that a thing you expect to be free from all future wear and tear?
Let's be clear: you're not getting a vacuum we dragged out of a swamp. You're getting a "scratch and dent" vacuum, which is a thing that isn't perfect, but isn't rebuilt or refurbished either. It a vacuum that has some cosmetic issues and can't be sold as new, but kinda sorta is. And since your vacuum is going to be down there in the dirt anyway... maybe that's okay?