According to Wikipedia, gerrymandering is the:
practice intended to establish an arguably unfair political advantage for a particular party or group by manipulating the boundaries of electoral districts, which is most commonly used in first-past-the-post electoral systems.
According to Wikipedia's page on Redistricting in the United States:
Redistricting in the United States is the process of drawing electoral district boundaries. A congressional act enacted in 1967 requires that representatives be elected from single-member districts.