reliable; spotless; trustworthy;
someone or something that is dependable and uncorrupted.
The story was unimpeachable because there were many witnesses who saw the same thing.
unimpeachable reminds of impeach.
we impeach someone when they are dishonest.
impeach means to remove someone from power.
they cannot be impeached because they are honest.
they are- un impeachable.
The results of the testing are unimpeachable. We get the same results each time.
(c) 2015 E. Carruthers