cistern

Noun

cistern (plural cisterns)

1. A reservoir or tank for holding water, especially for catching and holding rainwater for later use.
   • For cistern valves, they are well adapted—opening the full area upon the least descent of the ball, and are not liable to be set fast.1847, editorial staff, “Improvement in Water Taps, Cister Valves, &c. ”, in Scientific American, series 1, Volume 3, Issue 9, page 68
   • Their extreme necessity is attested by the countless number of old, unused cisterns with which the Holy Land is literally honeycombed.1913, A.C. Cotter, Catholic Encyclopedia, "Wells in Scripture"

   Synonyms:

   conservatory

2. In a flush toilet, the container in which the water used for flushing is held; a toilet tank.
   • It is possible to connect your tank to your toilet cistern and/or garden, so that even if the water is not drinkable it still can be used productively to make major water savings.2003, Allan Windust, chapter 9, in Waterwise House & Garden: a Guide for Sustainable Living, →ISBN, page 36
3. A shallow, typically oval, vessel made of porcelain, pottery, or glass.
4. The receptacle that holds the fuel in an oil lamp.
   • By next winter he was spending every evening poring over the work of Théodore Agrippa d'Aubigné on the French Reformation by the light of a little oil lamp, with a tiny cistern the size of an orange and no chimney[.]1977, K.M. Elizabeth Murray, Caught in the Web of Words, Oxford: Oxford University Press, page 22
5. A cisterna.
6. The vessel surrounding the condenser in a steam engine.