tiny amount; the slightest bit
Emphatic expression for an extremely small quantity, often used in negative or conditional contexts to mean 'not even a tiny bit'.
There is not a shred of truth in his story.
We cannot waste even the slightest bit.
A yojijukugo composed of 一 (one), 糸 (thread), 一 (one), and 毫 (fine hair), literally 'one thread, one fine hair', metaphorically indicating an extremely tiny amount.