preposterouspre‧pos‧ter‧ous /prɪˈpɒstərəs $ -ˈpɑːs-/ adjective formal 
Word Origin
The whole idea sounds absolutely preposterous!—preposterously adverb—preposterousness noun [uncountable]
Word OriginWORD ORIGINpreposterous
ExamplesOrigin:
1500-1600 Latin praeposterus ‘with the back part in front’, from prae- ( ➔ PRE-) + posterus ( ➔ POSTERIOR1)EXAMPLES FROM OTHER DICTIONARIES
Thesaurus- a preposterous excuse
- It's a preposterous claim that the government is trying to poison its citizens.
- It is preposterous that Bruce did not know that we were there.
- Ticket prices for football games are absolutely preposterous!
- But that said, the diesel costs £16,600, which is downright preposterous.
- Daunting and preposterous as the task appeared, I was glad to be busy again, of use.
- It seems preposterous that Bruce did not know we were there.
- It sounded utterly preposterous but it led to a longer silence.
- Many voters are ready to believe anything of them both, no matter how preposterous or sinister.
- So what Raskin proposed actually seemed preposterous.
- The very idea is preposterous and I was overjoyed to see that you believed me.
- Tuesday, Rana Kern again called those allegations preposterous, and said that as a pagan she worships the Earth.
Longman Language Activatorwhen something seems very unlikely to be true► unbelievable
completely unreasonable or silly SYN absurd: difficult or impossible to believe: · The things he had heard about her were almost unbelievable.it is unbelievable how/that: · It's unbelievable how nasty people can be.· I find it unbelievable that Mr. Carey does not remember the meeting at all.
► unlikely a story, explanation, or excuse that is unlikely cannot be believed because it is so unusual: · That sounds a pretty unlikely story to me!· Students invent all sorts of unlikely explanations as to why they can't do their homework.it is unlikely (that): · I think it's unlikely that the police had anything to do with it.highly unlikely: · It's highly unlikely that Burton will be the party's nominee.
► improbable a statement or event that is improbable is difficult to believe, even though it may in fact be true or may actually have happened: · The Rockets managed an improbable victory in last night's game.it is improbable that: · It's improbable that she would have been so successful without famous parents.highly improbable: · It's highly improbable that someone would win the lottery twice.
► implausible a statement or explanation that is implausible is difficult to believe because it is not like the way things usually happen: · Jill says she can earn $50,000 from the job, but this is an implausible figure.· The idea that a virus could wipe out an entire city so quickly seems a little implausible.
► incredible something that is incredible is so surprising or strange that it is difficult to believe, even though it is probably true: · This factory was capable of producing an incredible 100 cars per hour.it is incredible that: · It is incredible that the police still haven't caught him.
► inconceivable something that is inconceivable is so surprising or strange that it seems you cannot believe that it could possibly happen or be true: · The amount of time and money they have wasted on the project is inconceivable.it is inconceivable that: · It's inconceivable that university officials would fire someone as talented and loyal as Professor Schultz.
► unconvincing ideas, statements, and excuses that are unconvincing do not seem to be true or right and you cannot be persuaded to believe that they are: · Peter came to me with a rather unconvincing apology.· Their denial was unconvincing in view of the physical evidence linking them to the bombing.
► far-fetched an idea, story, or explanation that is far-fetched is difficult to believe because it sounds so surprising, unusual, or impossible: · The idea of travelling to other solar systems may sound far-fetched but scientists now see it as a real possibility.· His lawyers argue that the charges are based on a far-fetched conspiracy theory.
► preposterous formal an idea, story, or explanation that is preposterous is impossible to believe because it sounds completely unreasonable: · It's a preposterous claim that the government is trying to poison its citizens.it is preposterous that: · It is preposterous that Bruce did not know that we were there.
► lame an excuse or explanation that is lame is difficult to believe, because the person who says it has not tried hard enough to make it sound true: · She's always got some lame excuse for being late.· It sounded lame but I really had lost my ticket.
The whole idea sounds absolutely preposterous!—preposterously adverb—preposterousness noun [uncountable]