taru-adjective, adverb taking the 'to' particle
dejected; dispirited; crestfallen
Literary, somewhat old-fashioned word describing a visible state of dejection or discouragement. Often used with として or たる to modify a noun or verb.
彼は悄然としてうつむいていた。
He hung his head dejectedly.
悄然たる面持ちで部屋を出た。
He left the room with a crestfallen look.