The phrase "patent unreasonableness" means an extreme level of unreasonableness or irrationality. It refers to a decision, action, or behavior that is so obviously unreasonable that it is difficult to comprehend or justify. Full definition
Depending on the degree of deference indicated by the examination of the four factors, one of the following standards was applied by the reviewing court: the highly interventionist standard of correctness, the moderately deferential standard of reasonableness simpliciter, or the highly deferential standard of patent unreasonableness. (erudit.org)
The chambers judge did not address whether WCAT had the authority to reconsider the original decision for patent unreasonableness. (slaw.ca)