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avagy másik ötlet: "érvágás"

A Wikipedia szerint:
"Gazumping" is the refusal to formalise a property sale agreement at the last minute, usually in order to accept a higher offer.
http://en.wikipedia.org/wiki/Gazumping

Erre (is) mondják magyarul, hogy valaki eláll az üzlettől...

I don't think we have a similar one-word term for this English term.
It needs to be explained.


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Note added at 4 hrs (2010-09-13 15:48:46 GMT)
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To Amanda:

I think in the term "gazumping" the main concept is that there is a verbal agreement between the seller and the buyer about the price and after this verbal agreement the seller (NOT the buyer - this is very important) raises this price (higher than the agreed price). It means basically raising the price after a verbal agreement. When we talk about ráígérni that's a totally different concept. It means to bid. Not the seller raises the price, but buyer. Ráígérni is a word used in auctions also. It means that people who are buying (not selling - very important!) are saying a higher price just because they want that product/house etc. so much. So the concept is reverse in ráígérni, because not the seller tells a higher price, but the buyer. So it means bidding. Elállás means deciding not to make a business with the seller.

I don't know which of these meanings you need. Maybe if you give the exact sentence, it would be more obvious. As you can see Wikipedia gives more different meanings for gazumping.
So the exact context would help a lot.

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Note added at 4 hrs (2010-09-13 16:00:51 GMT)
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Answer to Amanda:

I referred to that even in English it had different meanings. If you check for example the Wikipedia link what you gave that link gives 3 different meanings and if you check this link (http://en.wikipedia.org/wiki/Gazumping ) it gives the 4th meaning of gazumping. Since in Hungarian we don't have such a "universal word" as gazumping (as many meaning of the English word so many different words in Hungarian), it would be good to know the exact sentence, then it would be easier to narrow down which of the meanings you exactly need. Context is very important in translation.

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Note added at 5 hrs (2010-09-13 16:40:02 GMT)
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To Amanda:

You said: "Yes you are right, it is confusing, they should at least agree on the English meaning!"

I try to be more clear. The given meanings are correct, they shouldn't agree on the English meaning, since a word (a term) can have different meanings. This is absolutely a normal case. 1 words have different meanings. You have to know which of the English meanings you need. If you tell the exact sentence, in which the term "gazumping" appears (this is called context), then you or we can narrow down the meaning of gazumping.

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Note added at 5 hrs (2010-09-13 16:52:03 GMT)
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Typo: 1 word can have different meanings.

I believe the key here is that the seller, having agreed verbally on a sale price with someone, accepts a higher offer from someone else. Since this takes place prior to signing the purchase and sale agreement, it cannot be disputed or deemed a breach of contract (since there is none, at this time).

Gazumping is the term used to describe this situation where the seller of an asset accepts a purchase offer, having already accepted another lower offer from another potential buyer. In other words, the seller changes his deal to sell to a second buyer who offers more money.

"... gyakori problémák az otthon eladással és vásárlással kapcsolatban
a) kapcsolt résztvevők, ingatlanközvetítők, meghiúsulás ráígérés miatt (gazumping), hitelezők, ajánlatok, ingatlan, ügyvédek és tulajdonba adás, ingatlanbecslés és értékelés..."

"... korrekt áron hirdetett, de mint kiderült a megállapodás után visszakozott, ráígérés miatt."

"1795 után a csákányi Batthyány-család, a Rába-völgy nagy földbirtokosa "ráígérés " útján meg akarta szerezni azt az előjogot..."

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Note added at 20 hrs (2010-09-14 07:27:19 GMT)
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In the light of the additional info, it seems like we can almost forget about the originally indicated field (real estate market). This may or may not work in the context but perhaps you could try "mismásolás"? Gazumping and gazundering.... they just sound so casual, especially in this context (two old ladies chatting about matters of the world). It almost doesn't really matter which way you look at it (from the buyer's or the seller's point), it's all that gazumping and gazundering going on these days..
http://www.guardian.co.uk/money/2001/sep/13/factsheetsonmovi...
These acts are not illegal but definitely not fair or ethical, either. So, "mismásolás" or "csűrcsavarás" might cover both. Or perhaps combine the two and just use "kupeckedés".. That works on any market and covers all unfair dealings. :)