1. a monstrous dog, especially one from hell or mythology, often depicted as fierce and supernatural
Usage: literary; mythological
2. a cruel, vicious, or relentless person
Usage: figurative; informal

Examples

• In Greek mythology, Cerberus was a three-headed hellhound guarding the gates of the underworld.
• The legend spoke of a hellhound that prowled the moors at night, terrorizing travelers.
• He was called a hellhound for his ruthless business tactics and complete lack of mercy.
• The old stories warned children about the hellhound that would come for the wicked.
• She described her former boss as a hellhound who made everyone's life miserable.
• Medieval manuscripts depicted hellhounds as demons with glowing eyes and sulfurous breath.