monstrance
Concise Oxford English Dictionary © 2008 Oxford University Press:
monstrance /ˈmɒnstr(ə)ns/
▶noun (in the Roman Catholic Church) an open or transparent receptacle in which the consecrated Host is exposed for veneration.
– origin ME (also in the sense ‘demonstration or proof’): from med. L. monstrantia, from L. monstrare ‘to show’.
'monstrance' also found in these Oxford entries:

