1. A reason or justification that is based on solid evidence, facts, or logical support; a cause that is properly substantiated
The court dismissed the case because the plaintiff had no well-founded reason for the lawsuit.
O tribunal rejeitou o caso porque o demandante não tinha uma razão bem fundamentada para a ação judicial.
2. A legitimate basis for belief, action, or concern that is supported by credible information
There is a well-founded reason to believe that climate change is accelerating.
Existe uma razão bem fundamentada para acreditar que as mudanças climáticas estão acelerando.