verb

• (British) To swindle; to extort.
• (British, Australia, real estate) To raise the selling price of something (especially property) after previously agreeing to a lower one.
  "If one believes that morality plays no part in such a transaction, and that the law is all that prevails, then I believe society is the poorer. Clearly no surveyor refuses to act for a client who gazumps — but while the practice is legal it can hardly be described as moral, and the position of the surveyor is far from clear."
• (British, Australia, real estate) To buy a property by bidding more than the price of an existing, accepted offer.
  "I can disclose that Mrs Blair had an offer of £2,765,000 accepted on a five-storey Georgian house in a fashionable area of central London, which she planned to give to daughter Kathryn.¶ However, actress Talulah Riley, 31, who played spoiled Annabelle Fritton in two St Trinian’s films, gazumped her with an offer of £3 million — a staggering £235,000 more than the asking price."
• (British, Australia) To trump or preempt; to reap the benefit underhandedly from a situation that someone else has worked to create.
  "The tactic was to gazump the Labour Party and the FOL by a major restructuring of the tax system."

noun

• (British, Australia, real estate) The act of gazumping.

noun

• (US, slang, dated) An automobile.
  ""Phoney" Thorpe, '06, and "Shorty" Winchester, '01, have been driving their "90 HP Gazumps" through the wilds of New Jersey, but otherwise keeping on the job."