"Definitive proof" means strong and convincing evidence that is clear, undisputable, and leaves no room for doubt. It is the most reliable and final evidence that can settle a question or prove something beyond any uncertainty. Full definition
Though we recognize that we have not provided definitive proof, this is the only hypothesis that receives any empirical support. (educationnext.org)
The study is careful to note that the results can not be taken as definitive proof of Teach to One's causal impact because the study lacked an experimental design. (educationnext.org)
Remember, the above list is not definitive proof of cancer. (pettao.com)