dead end
US /ˈded end/
UK /ˈded end/

1.
a road or passage that has no exit
:
•
The car turned into a dead end street.
•
We followed the path until it became a dead end.
2.
a situation or course of action that leads to no further progress
:
•
The investigation reached a dead end.
•
His career seemed to hit a dead end.