na-adjective, noun
providential protection; divine favor that keeps one alive
Refers to the idea that one's life is preserved by divine or fateful protection, often used in expressions of gratitude for having survived a dangerous situation.
あの事故で無事だったのは、まさに命冥加だ。
It was truly providential protection that I survived that accident.
冥加 alone means divine protection or grace, but 命冥加 specifically emphasizes the protection of one's life.
Compound of 命 (life) and 冥加 (divine protection). The exact historical derivation is uncertain, but the word is associated with Buddhist and folk beliefs in unseen protection.