unreason

UK: /ʌnˈriːz^ən/ US: (un rē′zən)

WordReference Random House Unabridged Dictionary of American English © 2025

un•rea•son  (un rē′zən), n. 

1. inability or unwillingness to think or act rationally, reasonably, or sensibly;
   irrationality.
2. lack of reason or sanity;
   madness;
   confusion;
   disorder;
   chaos:
   a world torn by unreason.

v.t. 

3. to upset or disrupt the reason or sanity of:
   The devious plot soon unreasoned the general.

• Middle English un-reson. See un-¹, reason 1250–1300

Collins Concise English Dictionary © HarperCollins Publishers::

unreason / ʌnˈriːz^ən/ noun

1. irrationality or madness
2. something that lacks or is contrary to reason
3. lack of order; chaos