по-чёрному

Adverbial form of чёрный (čórnyj, “black”), compare the usage in German schwarz, as in schwarzarbeiten (“to work illegally, lit.: to work black”)

• IPA^(key): [pɐ‿ˈt͡ɕɵrnəmʊ]

по-чёрному • (po-čórnomu)

1. (of ovens) without a chimney when a smoke goes directly into the house
2. (colloquial) illegally, without a permit; secretly

   рабо́тать по-чёрному ― rabótatʹ po-čórnomu ― to work cash in hand

3. (colloquial) severely; cruelly; mercilessly

   Их за э́то би́ли по-чёрному.

   Ix za éto bíli po-čórnomu.

   They were beaten mercilessly for that.