Preposterous is an adjective used to describe something that is absurd, ridiculous, irrational or nonsensical. It is an extreme word which connotes a sense of disbelief. There are several synonyms for this word, including outrageous, ludicrous, unbelievable, laughable, ridiculous, farcical, and nonsensical. All of these words express the same level of incredulity and are used to describe circumstances or gestures that are unbelievable, improbable, or foolish. Additionally, other synonyms for preposterous include foolish, asinine, and illogical. These words are commonly used in everyday language to describe things that are beyond reason or belief.