to select from among the worst; to choose from what is left over. You've bought a bad-looking car. You really scraped the bottom of the barrel to get that one. The worker you sent over was the worst I've ever seen. Send me another—and don't scrape the bottom of the barrel.
tv. to utilize the last or only things or people available, even if unsatisfactory. (see also bottom of the barrel.) They were really scraping the bottom of the barrel when they picked you.