ir ‧ ra ‧ tion ‧ al AC /ɪˈræʃ ə nəl/ BrE AmE adjective
[ Word Family: noun : ↑ rationality ≠ ↑ irrationality , ↑ rationale , ↑ rationalism , ↑ rationalist , ↑ rationalization ; adjective : ↑ rational ≠ ↑ irrational , ↑ rationalist ; verb : ↑ rationalize ; adverb : ↑ rationally ≠ ↑ irrationally ]
not based on clear thought or reason SYN unreasonable OPP rational , reasonable :
an irrational fear of flying
He’s becoming increasingly irrational.
—irrationally adverb
—irrationality /ɪˌræʃəˈnæləti, ɪˌræʃəˈnælɪti/ noun [uncountable]