Wiktionary
a. 1 contrary to reason; lacking an appropriate or sufficient reason; irrational. 2 Lacking the ability to reason. 3 (context often philosophy English) Not within the domain of what can be understood or analyzed by reason; outside the competence of the rules of reason. 4 (context economics social sciences public policy English) Not based on one's own interests; inconsistent with utility maximization. alt. 1 contrary to reason; lacking an appropriate or sufficient reason; irrational. 2 Lacking the ability to reason. 3 (context often philosophy English) Not within the domain of what can be understood or analyzed by reason; outside the competence of the rules of reason. 4 (context economics social sciences public policy English) Not based on one's own interests; inconsistent with utility maximization.
Usage examples of "non-rational".
I think if we can get him enthused enough about some project, his non-rational periods will decrease, maybe stop altogether.