taru-adjective, adverb taking the 'to' particle
strong (smell); pungent; fragrant
Describes a smell that is strong and noticeable, often a good or rich fragrance. Used as a 'taru' adjective or adverb with と.
部屋には花の香りが芬々と漂っていた。
The fragrance of flowers hung strongly in the room.
彼女が通ると、芬々たる香水の匂いがした。
When she passed by, there was a strong scent of perfume.
The word is formed by reduplication of the kanji 芬 (fragrance) with the reading ふん, creating an emphatic mimetic-like expression. The exact historical derivation is uncertain, but it is used in literary contexts to describe a strong, usually pleasant smell.