1. An area of land near or along a border between two countries or territories
The frontier region between the two nations was sparsely populated.
A região fronteiriça entre as duas nações era pouco povoada.
2. A remote or undeveloped area at the edge of settled territory
Pioneers settled in the frontier region seeking new opportunities.
Os pioneiros se estabeleceram na região fronteiriça em busca de novas oportunidades.
3. An area representing the limits of knowledge, technology, or exploration
Quantum physics is at the frontier region of modern science.
A física quântica está na região fronteiriça da ciência moderna.