I think it depends on context:
If BestBuy says it, it probably means you are looking at a demonstration unit. It was removed "out of its shipping box," and its packaging tape stripped off, ready to use. It may or may not still have its original accessories, etc. Or, the unit may have been sold and them returned, or repossessed. You don't get the box.
If the manufacturer says it, it probably means YOU can open and take it out of its box, strip off some light packaging, and be Ready to Go. Fully Assembled. Plug and Play.