On eBay and other online auctions, a sniper is that person that waits until the last second to bid on an item and take it away from you. In most cases, practicing sniping will get you an item for cheaper than if you would have depended on the proxy bidding systems (entering your max amount to begin with). Don't have the time to sit there and wait for the auction to end? There are many internet services and programs now that will bid on an item a few minutes (or seconds) before the auction ends. Aren't connected to the internet 24/7 and have a modem? Some even dial your modem for you.

When sniping first started to become popular, it was something many got mad about. Prior to sniping you had an idea of how much an item would sell for well before it's end. After sniping, it became very frustrating to see the item you thought you'd win for around $40 all of a sudden be lost in the last few seconds for $80. Some became so frustrated they even went on crusades, publicly refusing to snipe on moral grounds hoping that they could stem the sniping tide. Sniping has since become an established part of the online auction world, though.