Rejects
Quality is highly important to any designer brand, but at the same keeping down costs is something any business has to do. There is obviously a conflict between these two goals and how the brand manages this is by looking for a low cost factory, but then requiring that strict quality checking is done on finished garments.
Naturally some garments are going to fail this quality check, if they didn't then the brand would look for a cheaper factory, and sometimes if the brand has very high quality standards the "reject" items are actually perfectly wearable, but have slight issues only.
Typical reasons for rejecting would be inaccurate stitching, marks on fabric, badly positioned buttons and so on. At the extreme end things like blouses with two left sleeves are not unknown!
But for minor things such as asymmetrical stitching a typical buyer may consider it satisfactory. Or a misplaced button might be something that could be fixed. And hence it would still be a good buy for the budget conscious fashionista.
Rejected items typically have the brand label cut, slashed or holed in order to show that this item is not being sold under the "brand" it belongs to. Always look out for cut brand labels and examine the garment very carefully in good light to ensure that whatever quality issues there may be are acceptable to you.
Rejects are not like Overrun, End of Season or Samples in that they actually have something wrong with them. It's up to you to find out what, and decide if it is acceptable.