1. to make demands more rigid, harsh, or uncompromising; to increase the severity or strictness of requirements
The government decided to stiffen demands on environmental compliance.
O governo decidiu enrijecer as exigências de conformidade ambiental.
2. to strengthen one's position by making conditions or requirements less flexible
Union leaders voted to stiffen demands for better working conditions.
Os líderes sindicais votaram para enrijecer as exigências por melhores condições de trabalho.