adverb
stark-naked; completely naked
Literary or emphatic expression meaning 'without a single thread on one's body'. Often used in descriptive or dramatic contexts.
See also: 一糸まとわぬ (いっしまとわぬ)
彼は一糸まとわず湖に飛び込んだ。
He jumped into the lake stark-naked.
一糸まとわずの姿で写真を撮られた。
They were photographed completely naked.
From 一糸 (one thread) + まとわず (negative of まとう, to wear), literally 'not wearing a single thread'. The exact origin is uncertain, but it is a set phrase emphasizing complete nudity.