underground business

1) type of business in which you sell illegal products such as selling drugs, alcohol (in the places where it’s forbidden to buy) or weapons to people without a special license.
2) running a manufacture where illegal things are produced.

1) my friend deals drugs, so he runs an underground business.

2) A: she owns a great factory that produces foods with trans fats.
B: ohhh, as far as i’m concerned those fats are illegal so it must be an underground business.
A: that definitely is.