middle third of a two-hour period
Historical Japanese timekeeping term referring to the middle segment of a traditional two-hour unit (刻). Rare in modern usage, mostly encountered in historical contexts.
In the Edo-period time system, one koku was divided into three parts, and the middle part was called chūkoku.
Compound of 中 (middle) and 刻 (traditional Japanese time unit). The exact historical derivation is uncertain, but the term follows the pattern of 上刻 and 下刻 for dividing a two-hour period into thirds.