hecatomb
Concise Oxford English Dictionary © 2008 Oxford University Press:
hecatomb /ˈhɛkətuːm/
▶noun (in ancient Greece or Rome) a great public sacrifice, originally of a hundred oxen.
– origin C16: via L. from Gk hekatombē (from hekaton ‘hundred’ + bous ‘ox’).
'hecatomb' also found in these Oxford entries:

