What does "relentless" mean?

Relentless: Unmoved by appeals for sympathy or forgiveness; insensible to the distresses of others; destitute of tenderness; unrelenting; unyielding; unpitying; as, a prey to relentless despotism. For this the avenging power employs his darts,.. Thus will persist, relentless in his ire. Dryden. -- Re*lent"less*ly, adv. -- Re*lent"less*ness, n.