1. An expression used to indicate that if something is not justified in one case, it is even less justified in another case; used in logical argumentation to strengthen a negative conclusion
If we cannot trust him in small matters, com menor razão should we trust him with our savings.
Se não podemos confiar nele em pequenas questões, com menor razão devemos confiar-lhe nossas economias.
2. A rhetorical device meaning 'and certainly not' or 'much less'
He cannot even read in Portuguese, com menor razão write in English.
Ele nem consegue ler em português, com menor razão escrever em inglês.