na-adjective, taru-adjective, adverb taking the 'to' particle
Literary word describing a state that evokes pity or sadness. Often used in the adverbial form びんぜんとして or as a たる adjective in written Japanese.
彼の境遇はまことに憫然たるものがあった。
His circumstances were truly pitiable.
びんぜんとして涙を誘う話だ。
It's a story that moves one to tears with its pitifulness.
From Chinese 憫然 (mǐnrán). The exact historical derivation in Japanese is uncertain; it entered as a literary Sinitic compound.