Malapportionment

Etymology

From "mal-" (Latin "malus," bad) plus "apportionment," the act of portioning out (Latin "ad-" plus "portio," share). A term of art in political science and law, central to mid-twentieth-century “one person, one vote” cases in the United States.

noun · /mal-uh-POR-shuhn-muhnt/
The unequal distribution of representation, so that electoral districts contain very different numbers of voters and some votes count for more than others.
What it names
It gives a precise name to a quieter form of electoral distortion — unequal district size — that people often lump in with the more famous manipulation of district shape.
Example
Decades without redrawing lines left rural districts a tenth the size of urban ones — textbook malapportionment.
Related idea
Often confused with gerrymandering, but the two differ: gerrymandering manipulates the shape of districts to favor a group, while malapportionment concerns their size — unequal population per seat.