without one's knowledge; easily
Rare literary adverb meaning doing something without the person concerned knowing, or doing something effortlessly. Often used in the pattern 〜に.
He proceeded with the plan without anyone's knowledge.
She solved the difficult problem with ease.
Alternate kanji spelling without the repetition mark; less common.
Reduplication of 闇 (やみ, darkness), literally 'dark-dark', implying something done in the dark or without notice. The exact historical derivation is uncertain.