1. a tank or reservoir for storing water, especially rainwater collected from a roof
2. the water tank inside a toilet that holds water for flushing
Usage: common in British English

Examples

• The old farmhouse had a large cistern on the roof to collect rainwater.
• During the drought, many families relied on cisterns to store water for daily use.
• The cistern in the bathroom needs to be refilled after each flush.
• They installed a new cistern to capture runoff from the gutters.
• The cistern was made of concrete and could hold up to 5,000 gallons.
• She checked the cistern to see if there was enough water for the garden.