na-adjective, noun
Describes something so foolish or unreasonable that it is laughable or contemptible. Often used in formal or written contexts to express scorn.
彼の言い訳は笑止千万だ。
His excuse is utterly ridiculous.
そんな提案は笑止の沙汰だ。
Such a proposal is a laughable matter.
Compound of 笑 (laugh) and 止 (stop), literally 'stopping laughter', i.e., something so absurd it makes one stop laughing in disbelief. The exact historical derivation is uncertain.