noun
unlucky day; day of abstinence; death anniversary
In Onmyōdō, a day considered inauspicious for important activities; historically also referred to a death anniversary or a day of purification and fasting. The term is now rare and mostly encountered in historical or esoteric contexts.
See also: 陰陽道
陰陽道では、忌日には遠出を避けるべきとされた。
In Onmyōdō, it was said that one should avoid long journeys on an unlucky day.
この日は故人の忌日にあたるので、親族が集まっ
This day was the anniversary of the deceased's death, so relatives gathered.
Compound of 忌み (imi, 'abstinence, mourning') + 日 (hi, 'day'), with rendaku voicing. The exact historical development is uncertain, but the term is deeply associated with Onmyōdō practices.