黑咕隆咚

hēi gu lōng dōng

pitch-black

pitch-dark

黑

hēi

abbr. for Heilongjiang province 黑龍江|黑龙江[Hei1 long2 jiang1]

咕

gu

(onom.) for the sound of a bird, an empty stomach etc

隆

lōng

sound of drums

咚

dōng

(onom.) boom (of a drum)