cis·tern 
(sĭstərn)
(sĭstərn)n.
1. A receptacle for holding water or other liquid, especially a tank for catching and storing rainwater.
2. Anatomy A cisterna.
[Middle English cisterne, from Latin cisterna, from cista, box, from Greek kistē, basket.]
cis·ternal (sĭ-stûrnəl) adj.