irrational
adjective /ɪˈræʃənl/
  /ɪˈræʃənl/
- not based on, or not using, clear logical thought synonym unreasonable
- an irrational fear
 - You're being irrational.
 
Extra Examples- There was nothing inherently irrational in such a decision.
 - What is the reason for this seemingly irrational behaviour?
 
Oxford Collocations Dictionaryverbs- appear
 - be
 - seem
 - …
 
- completely
 - quite
 - totally
 - …
 
Word Originlate Middle English: from Latin irrationalis, from in- ‘not’ + rationalis (from ratio(n-) ‘reckoning, reason’, from rat- ‘reckoned’, from the verb reri).