secret language; code word; argot
dark side (of nature, town, etc.)
dark; gloomy; somber; depressing
light and darkness; light and shade
declaring a concealed kong; forming a concealed four-of-a-kind
reef; sunken rock; unforeseen difficulty
memorization; memorisation; learning by heart
dead of night; shades of night; black of night
(theatrical) blackout; taking a (sudden) turn for the worse; rapid deterioration
dark place; unlit spot; darkness
implicitly; indirectly; tacitly; by implication; obscurely
suspicion will raise bogies; once you suspect something, everything else will look suspicious; jumping at shadows
imbecility; feeblemindedness; dark
dark; gloomy; black; doleful; discouraged; disappointed
subterranean drain; culvert; conduit
secretly; covertly; tacitly
scent of a flower floating about in the air; lingering scent of a flower in the darkness
secretly; covertly; tacitly
dark hole; idiot; fool; historical road
dark figure (esp. of crime); dark number; hidden figure; difference between the actual and reported figure
concealed pung; concealed three-of-a-kind
subterranean drain; culvert; conduit