noun

• (Ancient Greece, Ancient Rome, historical) A great public sacrifice to the gods, originally of a hundred oxen; also, a great number of animals reserved for such a sacrifice.
  "O be propitious, powerfull God of Arts, / I sheathe my weapons, and doe breake my darts, / Be then appeas'd, I'le offer to thy shrine, / An Heccatombe, of many spotted kine."
• (by extension, religion, historical) A great public sacrifice in other religions; also, a great number of animals or people reserved for such a sacrifice.
  "The tutelary deity of the Aztecs was the god of war. The great object of their military expeditions was, to gather hecatombs of captives for his altars. The soldier, who fell in battle, was transported at once to the region of ineffable bliss in the bright mansions of the Sun."
• (figuratively, literary and poetic) A great number of animals, people, or things that are sacrificed or destroyed; any great sacrifice; also (generally), a large amount.
  "O hecatombe! O catastrophe! / From Mydas pompe to Irus beggery!"

verb

• (transitive) To provide (someone or something) with a hecatomb.