rotten boroughs

Noun

rotten borough (plural rotten boroughs)

1. (UK, historical) A parliamentary borough that was represented in Parliament although the number of voters had diminished so greatly that they were largely controlled by the main landowner; such boroughs were abolished in the 19th century.
   • […] Queen's Crawley was no longer so populous a place as it had been in Queen Bess's time—nay, was come down to that condition of borough which used to be denominated rotten–yet, as Sir Pitt Crawley would say with perfect justice in his elegant way, "Rotten! be hanged—it produces me a good fifteen...[1847 January – 1848 July, William Makepeace Thackeray, “Crawley of Queen’s Crawley”, in Vanity Fair […], London: Bradbury and Evans […], published 1848, →OCLC, page 57

   Synonyms:

   nomination borough, proprietorial borough

2. (UK, broadly) A parliamentary constituency or electoral district in a similar situation.