1. (in ancient Greece and Rome) a great public sacrifice of 100 oxen or cattle.
2. a large-scale sacrifice or slaughter
Etymology: from Greek hekaton, one hundred.
The first month of the Attic calendar was Hekatombaion, the month in which such sacrifices were made.
"By extension, a hecatomb is any large slaughter perpetrated for a consequent benefit. Natural selection is a long series of hecatombs."
- Stephen Jay Gould, "Eight Little Piggies: Reflections in Natural History"