Underwear one resorts to wearing only when in desperate need of doing laundry. Though these undergarments may be ugly, fit weirdly, or have holes, one has chosen not to throw them out just so they can serve this purpose. Such undergarments may be deemed unwearable for a regular day, but are still one step above re-wearing dirty underwear, allowing the user to postpone doing his laundry for one more day.
Guy 1: What the hell man... why are you wearing olive green boxers with a hole in the crotch?
Guy 2: They're backup boxers... I wasn't paying attention to how much underwear I had left and I ran out of good pairs.