British Slang.| 1. | to cheat (a house buyer) by raising the price, at the time a contract is to be signed, over the amount originally agreed upon. |
| 2. | an act of gazumping. |

Gazump
A situation in which the price for real estate or land is raised to a higher price than what was previously verbally agreed upon.
Investopedia Commentary
Basically, raising the price just before the papers are signed and the deal is delivered.
Related Links
20 Investments You Should Know
The REIT Way
See also: Gazunder, Land, Property, Real Estate