What does "merciless" mean?

Merciless: Destitute of mercy; cruel; unsparing; -- said of animate beings, and also, figuratively, of things; as, a merciless tyrant; merciless waves. The foe is merciless, and will not pity. Shak. -- Mer"ci*less*ly, adv. -- Mer"ci*less*ness, n.

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