taru-adjective, adverb taking the 'to' particle
deeply sad; grieving
Archaic literary word used in classical or poetic contexts; describes a state of profound sorrow or lamentation. Functions as a taru-adjective or adverb with と.
彼女は哀哀として、亡き夫を偲んだ。
She grieved deeply, remembering her late husband.
Reduplication of 哀 (あい, 'sorrow, grief'), an archaic Sino-Japanese morpheme. The exact historical derivation is uncertain, but the form follows a classical pattern of emphatic repetition.