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thread; strand; string
一糸いっし乱れみだれぬ行進こうしんを見せみせた。
They showed a march in perfect order.
彼女かのじょは一糸いっしも纏わまとわぬ姿すがただ。
She is completely unclothed.
一糸いっしの隙すきもない警備けいび体制たいせいだ。
It's a security system without any gaps.