noun
gloom; semi-darkness; dim light
Describes a state of partial darkness, often with a slightly negative or eerie nuance. Common in literary and descriptive contexts.
薄暗闇の中、人影が動いた。
A figure moved in the dim light.
部屋は薄暗闇に包まれていた。
The room was enveloped in semi-darkness.
薄暗い is an adjective meaning 'dim' or 'gloomy', whereas 薄暗闇 is a noun referring to the state of semi-darkness.
Compound of 薄 (usu, 'thin' or 'faint') and 暗闇 (kurayami, 'darkness'). The reading うすくらやみ is a straightforward combination of the readings of the components.