very small difference (esp. in time); tiny interval
Used when two events are separated by a very narrow margin, often in races, arrivals, or timing. Emphasizes a close call.
He missed the train by a split second.
The finish was decided by a hair's breadth.
The word タッチ (touch) is borrowed from English, and 差 means 'difference'. The phrase literally means 'a touch of difference', referring to a margin as small as a touch.