back alley 
noun
1A narrow passage behind or between buildings: we exited into a back alley via the fire door...
- Once in the city, she got lost immediately in the maze of back alleys and narrow lanes.
- Steve's is not the first complaint I have received about unwanted rubbish being left in the back alleys behind terraced homes.
- In this city the citizens run madly, ignoring the back alleys, tunnels and buildings of yesterday.
1.1 [as modifier] Secret and illegal: a back-alley abortion...
- Sadly, too many of them turn to back alley silicone.
- ‘But for that to happen a lot of women would have to start dying from back alley abortions,’ said another.
- Both of them said that they'd never have an abortion, but they don't want to go back to the days of back alley abortions and women dying.