The term 'insupposable' is an adjective meaning impossible to imagine or believe. It is derived from the Latin words 'IN' and 'supponere, ' which mean 'not' and 'to suppose, ' respectively. The two crossword solutions for this term are 'INCREDIBLE' (10 letters) and 'INCONCEIVABLE' (13 letters). Both of these words have similar meanings, with 'INCREDIBLE' meaning too extraordinary to be believed and 'INCONCEIVABLE' meaning beyond belief or understanding. Together, they provide a strong description of something that is impossible to imagine or believe.