blind alley

nouns

a street with only one way in or out
(figurative) a course of action that is unproductive and offers no hope of improvement
"all the clues led the police into blind alleys"; "so far every road that we've been down has turned out to be a blind alley"
domain usage
language used in a figurative or nonliteral sense
is a type of (narrower)
a mode of action
"if you persist in that course you will surely fail"; "once a nation is embarked on a course of action it becomes extremely difficult for any retraction to take place"