Last minute very high bid on
eBay or other online auction house meant to blow the competition out of the water. A blast bidder really wants the item and is smart enough not to tip
shem's hand to early. For a seller colliding blast bids provides a tidy profit.
Example: I blast bid $30 on the Gene Ammons LP even though I knew it wouldn't get higher than $20 because it rounds out my collection of Jug's vinyl.