1. to reduce or lessen the degree of confidence, assurance, or certainty about something
The new evidence began to diminish certainty about the original hypothesis.
A nova evidência começou a diminuir a certeza sobre a hipótese original.
2. to make something less certain or clear
Conflicting reports diminish certainty regarding the company's financial status.
Relatórios conflitantes diminuem a certeza sobre a situação financeira da empresa.