Lewis & Short

tĕnē̆brĭcōsus, a, um, adj. [tenebricus], full of darkness or gloom, shrouded in darkness, dark, gloomy (rare but class.): esse sensus non obscuros sed tenebricosos, Cic. Ac. 2, 23, 73: popina, id. Pis. 8, 18: libidines, id. Prov. Cons. 4, 8: tenebricosissimum tempus, id. Vatin. 5, 11: iter, Cat. 3, 11: locus angustus et tenebricosus, Varr. R. R. 3, 9, 19.