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1.
Manipulating the price of an e-bay auction by simply placing a bid with no intention to buy, but rather to increase price more rapidly for the seller. Should the bumper be the winner of the auction, they will be transafered the money by the seller after payment, and give him back his goods.

Sometimes this occurs when the bumper simply wants to annoy others by pushing the price to ridiculous amounts near the end of the auction so desperate bidders place higher bids. These people also enjoy pestering the seller with questions about thier sexuality and underwear hygeine.
Spotting e-bay bumping is quite hard, since many n00bs unintentionally push the price up by placing consequtive increasing amounts for the same item within minutes.

If you notice that an item has a bidder who has placed multiple bids for an item, check thier feedback. If you notice this person has bought several items over a long period of time from the current seller, you have probably uncovered a scam, and should report it.

Words related to e-bay bumping

n00b