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тёмное дело stresses
gen.	crook business; dark business; dubious transaction; shady enterprise; suspicious business
Makarov.	shady business; shady transaction
тёмные дела
gen.	discreditable practices; oblique dealings; the deeds of darkness; dirty tricks; monkeyshines
Makarov.	hole-and-corner dealings

тёмное дело: 23 phrases in 6 subjects

American usage, not spelling	1
General	12
Idiomatic	1
Informal	1
Makarov	6
Slang	2