cistern

noun

1. A container or large tank used to store water, especially rainwater or water for a supply system.

   B2

   countableformal

   • "The house has a large cistern for collecting rainwater."B1
   • "The ancient city used underground cisterns to store water during dry periods."C1
   • "In many rural areas, cisterns are used to provide water during dry seasons."B2
   • "The cistern was cleaned and repaired to ensure a safe water supply."B2

2. The tank in a toilet that holds the water used for flushing.

   B2

   countableUK

   • "The toilet cistern is leaking."B1
   • "The plumber replaced the faulty valve inside the cistern."B2