Real Dictionary

gerrymander in American English
a redistricting of voting districts to the advantage of one party or disadvantage of a group, region, etc.
to divide (a voting area) so as to give one political party a majority in as many districts as possible or weaken the voting strength of an ethnic or racial group, urban population, etc.
to engage in gerrymandering
noun: the dividing of a state, county, etc., into election districts so as to give one political party a majority in many districts while concentrating the voting strength of the other party into as few districts as possible
transitive verb: to subject (a state, county, etc.) to a gerrymander

gerrymander in British English
noun: an act or result of gerrymandering
verb: to divide the constituencies of (a voting area) so as to give one party an unfair advantage