It's returned merchandise. Technically it's used, and many times it's used and found defective in some way or just not wanted by the original buyer. On RMA, many times there's an incorrect reason for return and ob had put the item back in the package without any destruction, even using all the original packaging. I've seen this done to psus when someone couldn't find 1 cable, they buy a psu, steal the cable, return the item as unwanted/unused and it gets stuck back on the shelf, the returns staff having no clue there's a cable missing since the paperwork says its all there. The next buyer pretty soon discovers the missing cable, and complains, but cannot prove the cable was missing, newegg can only take their word for it. Sometimes, ppl deliberately lie about the missing cable, because they needed one, couldn't find one online, didn't want to pay for one so cheat newegg out of a cable by complaining one was missing so the psu is obviously used.
Newegg can't prove they didn't sell a used item, complainers can't prove they aren't trying to scam newegg. Take stuff with a grain of salt.