absurd; unreasonable; out of the question
A strong, somewhat old-fashioned expression meaning something is so unreasonable it is not even worth considering. Often used in formal or literary contexts.
Such a demand is out of the question.
His proposal was dismissed as preposterous.
沙汰 (matter, affair) + の + 外 (outside). Literally 'outside the matter', meaning something is beyond consideration or reason. The exact historical derivation is uncertain, but the phrase has been used in classical and literary Japanese.