gazump

Concise Oxford English Dictionary © 2008 Oxford University Press:
gazump /gəˈzʌmp/

▶verb Brit. informal make a higher offer for a house than (someone whose offer has already been accepted) and thus succeed in acquiring the property.

– derivatives
gazumper noun.

– origin 1920s (in sense ‘swindle’): from Yiddish gezumph ‘overcharge’.