taru-adjective, adverb taking the 'to' particle
Literary, somewhat archaic word describing something in a state of absolute purity, without any mixture or flaw. Often used adverbially with と (e.g., 醇乎と) to modify a verb or adjective.
彼の芸術は醇乎として一点の曇りもない。
His art is pure and without a single blemish.
その酒は醇乎たる味わいで、雑味がまったくなかった。
The sake had a pure, unadulterated flavor with no off-tastes at all.
Compound of 醇 (pure, rich) or 純 (pure) and the classical adverbial suffix 乎 (こ), forming a literary adjective/adverb. The exact historical derivation is uncertain; the spelling is conventionally associated with purity.