Auction sniping is a technique where a user in a timed online auction waits until the time limit is nearly expired before entering a bid. The other participants in the auction do not have enough time to enter a counterbid, allowing the sniper to win the auction. A sniper may enter the bids manually or use a software package to do so.
Auction sniping may also be known as bid sniping.
Techopedia explains Auction Sniping
Auction sniping is a legitimate way to get an item without engaging in a bidding war, but it does cause hard feelings among the other bidders. Online auction sites have taken some steps to minimize the prevalence of sniping, including requiring a CAPTCHA before entering a bid and adding a "buy now" button for bidders who are willing to forgo the auction process to leave with the item.