Definition of preposterous adjective from the Oxford Advanced Learner's Dictionary

     

    preposterous

     adjective
    adjective
    BrE BrE//prɪˈpɒstərəs//
     
    ; NAmE NAmE//prɪˈpɑːstərəs//
     
    (formal)
     
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  1. 1completely unreasonable, especially in a way that is shocking or annoying synonym outrageous These claims are absolutely preposterous! It’s preposterous to suggest that everything was her fault! The whole idea sounds quite preposterous!
  2. 2unusual in a silly or shocking way synonym outrageous The band were famous for their preposterous clothes and haircuts.
  3. Word Origin mid 16th cent.: from Latin praeposterus ‘reversed, absurd’ (from prae ‘before’ + posterus ‘coming after’) + -ous.
See the Oxford Advanced American Dictionary entry: preposterous