Today's Word of the Day means...
cisterna cis·ter·na (sĭ-stûr'nə)
n. pl. cis·ter·nae (-nē')
A cavity or enclosed space serving as a reservoir, especially for chyle, lymph, or cerebrospinal fluid.
An ultramicroscopic space or channel occurring between the membranes of the flattened sacs of the endoplasmic reticulum, the Golgi complex, or the two membranes of the nuclear envelope.