The word preposterous means absurd, impossible. When you say something is preposterous, you are saying that it is impossible for that to be the case.
The idea of preposterous is to set something up so that it cannot possibly be true.
The preposterous idea was that he could fly.
adjective
so unreasonable as to invite derision
Synonyms:
1
The notion is preposterous.
2
This is preposterous aggrandizement.
3
The claim is clearly preposterous.
4
The whole situation is preposterous.
5
In the case of charcoal, the notion is preposterous.
6
Preposterous things happen in the world.
7
The claims of the article are quite preposterous
8
The rest of your comments are preposterous.
9
The reality sunnily undermines the preposterous fantasy.
10
At the time he said that, the idea seemed preposterous.