taru-adjective, adverb taking the 'to' particle, na-adjective, noun
Formal, literary, and somewhat dated term describing a scene or feeling of profound loneliness and emptiness. Often used in written descriptions of landscapes or emotional states. The reading せきばく is a variant.
See also: 寂寞 (せきばく)
寂寞とした荒野が広がっていた。
A desolate wilderness stretched out.
彼は寂
He sank into a feeling of loneliness.
The exact derivation is uncertain; the kanji 寂 (lonely, quiet) and 寞 (lonely, still) combine to reinforce the meaning of profound stillness and loneliness.