full moon; 15th day of the lunar month
Archaic noun; in modern Japanese, 満月 (まんげつ) is used for 'full moon' and 十五夜 (じゅうごや) for the 15th night of the lunar month. The reading もち is rare and mostly found in classical contexts.
In classical texts, 望 is read as もち and can refer to the full moon.
旧暦の十五日を「もちの日」と呼ぶことがあった。
The 15th day of the lunar month was sometimes called 'mochi no hi'.
望 refers to the full moon phase, the opposite point in the lunar cycle from 朔, the new moon.
Archaic kanji spelling for the reading もち, meaning 'full moon' or the 15th day of the lunar month.
The reading もち for 望 is archaic and its exact derivation is uncertain; it is not related to the common word 餅 (もち, rice cake). The kanji 望 carries meanings of 'full moon' and 'hope', but here it is used in its lunar sense.