Flashed is usually a term for firmware/software upgrade ie "I downloaded the new software for my router and flashed it".
In the context of legit devices, they often have new firmware available to them, but in the case of my MIFI, you could not download the firmware from a website, you had to activate it with the original carrier it was bought thru and it would download over the air and flash the first time it is used.
If these MIFI devices are being marketed as "unlocked" as well, knowing it has been flashed would be an important selling point for someone who has no intention of ever putting a Verizon SIM in a Verizon branded MIFI.
