preposterous
adj.adj. completely silly or impossible to believe. You use this when an idea or situation is so strange that it makes no sense at all.
adj. contrary to reason or common sense; utterly absurd or ridiculous. Often used to express strong disbelief or indignation regarding a proposal or claim.
The idea that the moon is made of cheese is preposterous.
It is preposterous to suggest that a professional athlete could survive on a diet of only candy.
The defense attorney argued that the prosecution's timeline was preposterous, as it required the defendant to be in two cities simultaneously without any means of rapid transport.
From Latin praeposterus (“with the hinder part before, reversed, inverted, perverted”), from prae (“before”) + posterus (“coming after”).
Often used predicatively after linking verbs like 'be', 'sound', or 'seem'.