A large opening in the subarachnoid space filled with cerebrospinal fluid, and located between the cerebellum and the back of the medulla oblongata.
It is the largest of the subarachnoid cisterns. It is one of the three principal openings in the subarachnoid space; the other two are pontine cistern and interpeduncular cistern.
Also called: cisterna cerebellomedularis.
See also: pontine cistern, interpeduncular cistern.