street drug 

Any type of drug and/or medication that is illegally sold and bought

I didn't think adderall was a "street drug" since it's meant for people to stay focused, but later found out that it is since it is illegally bought and sold on the street and addicting as well.

street drug by Wisdom Truth April 14, 2014

A dangerous street drug 

crack

You see what I did there. I reversed the definition

(A dangerous street drug)

A dangerous street drug by Dubiks December 22, 2018