(noun) a street with only one way in or out. Synonyms: blind alley, cul de sac, dead-end street, impasse.
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Noun Definition 1
(noun) (figurative) a course of action that is unproductive and offers no hope of improvement. Synonyms: blind alley. Examples: "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."