1. continuing without stopping or becoming less intense; persistent and determined
2. showing no mercy or compassion; harsh and unforgiving

Examples

• The detective’s relentless pursuit of the truth finally solved the case.
• She faced relentless criticism from her opponents during the campaign.
• The relentless rain flooded the streets for three days straight.
• His relentless work ethic helped him succeed in business.
• The army launched a relentless attack on the enemy fortress.
• The relentless heat made it impossible to work outside.
• Despite relentless pressure, she refused to give up her principles.