1. Someone who disagrees with an assertion in a controversial political debate: Judy turned out to be a denialist in the local government when she opposed the statement made by the chairman to be unsatisfactory and incorrect concerning the kindergarten that was to be built.
2. Anyone who has increasingly come to maintain personal beliefs even in the face of solid scientific evidence: A denialist refers to a person who opposes a range of issues from childhood vaccines to genetically modified foods, maintaining that living in a totally natural and healthier way is better.

Referring to a negation in a political dispute, conflict, or contention: In the denialist movement to activate people to save the environment, as apposed to so many businesses and politicians, there were not only many young people, but many parents and grown-ups as well.