When it comes to synonyms for the word "insupposable," there are several options that can be used interchangeably. Some common synonyms for this word include inconceivable, unimaginable, incredible, unbelievable, impossible, and implausible. Each of these words shares a similar meaning to "insupposable," which essentially indicates that something is difficult or impossible to believe or accept. Other possible synonyms for "insupposable" might include the words unreal, fantastical, or even absurd, depending on the context in which this word is being used. Regardless of which synonym you choose, each one can be used to convey a sense of disbelief or incredulity about a particular idea or statement.