Definitions for darklyˈdɑrk li
Random House Webster's College Dictionary
so as to appear dark.
in a vaguely threatening or menacing manner:
to hint darkly of hidden dangers.
Origin of darkly:
darkly, in darkness(adverb)
"the river was sliding darkly under the mist"
in a dark glowering menacing manner
"he stared darkly at her"
to appear as dark
faintly seen in the dark
Origin: dark + -ly
with imperfect light, clearness, or knowledge; obscurely; dimly; blindly; uncertainly
with a dark, gloomy, cruel, or menacing look