rotten borough
noun
- Brit. historical a borough that was able to elect an MP though having very few voters, the choice of MP typically being in the hands of one person or family〈英, 史〉腐败选区（虽然选民寥寥无几但仍能选举议员的选区, 议员的选举通常被一个人或一个家族所控制）。
词源
so named because the borough was found to have 'decayed' to the point of no longer having a constituency.