Definitions

1. adjective

unquestionable or not open to doubt; unshakeable

“The evidence presented in the court case proved the suspect’s guilt to be undubious.”

2. adverb

in an undoubtable or unquestionable way

“She worked undubiously to complete the project on time.”

3. noun

something that is unquestionable or not open to doubt

“The team’s victory in the championship match was an undubious achievement.”