Denialism is when a person or group denies a theory, law or fact of a well established discipline. It is the methodological school of woo. It is the art of denying a well evidenced fact in an authoritative way, despite lack of any empirically acceptable counter-evidence.
In scientific denialism, the denialist can deny a cause (carbon dioxide does not cause global warming), an effect (global warming does not occur), the association between the two (the earth is warming, but not because of carbon dioxide), the temporal relationship (carbon dioxide concentrations are increased because the earth is warming) or the isolation of the cause-and-effect relationship (other factors than greenhouse gases cause the earth to warm). Often denialists will practice minimization (the earth is warming, but it's not harmful) and will use misplaced skepticism in the veneer of being a scientist when it is unwarranted.