(o-sā’ri-um), n,; pl. ossaria (-iä). [LL.: see ossuary.] An urn or other receptacle for the bones or ashes of the dead; an ossuary.

Source: Century Dictionary Online.

“Keep your eye on that spot,” William said to me. “There could be a passage leading to the Aedificium.”

“Under the cemetry?”

“And why not? In fact, now that I think about it, there must be an ossarium somewhere; they can’t possibly have buried all their monks for centuries in that patch of ground.”

Source: The Name of the Rose by Umberto Eco.