Webster's Revised Unabridged Dictionary · 1913

Darkling

Darkling (dark"ling) , adverb

[Dark + the adverbial suffix -ling.]

In the dark. [Poetic]
So, out went the candle, and we were left darkling. — Shakespeare
As the wakeful bird Sings darkling. — Milton

Darkling , present participle and adjective

1.
Becoming dark or gloomy; frowing.
His honest brows darkling as he looked towards me. — Thackeray
2.
Dark; gloomy.
The darkling precipice. — Moore