taru-adjective, adverb taking the 'to' particle
Literary word describing a scene or atmosphere that is barren, lifeless, and emotionally cold. Often used with たる or として.
冬の荒野は索漠たる風景だった。
The winter wilderness was a desolate landscape.
彼の心は索漠として、何も感じられなかった。
His heart was bleak and he could feel nothing.
The exact derivation is uncertain; the kanji 索 (search, rope) and 漠 (vague, desert) together convey a sense of vast emptiness and bleakness.