a blind alley

1. The end of a road, path, or other passage that does not have an exit or other passages attached to it; a dead end. Because the GPS brought us to a blind alley, we'll have to turn around and take that side road. We're at a blind alley. We'll have to turn around and take that side road Are you sure this is where the directions said to go? Because it sure looks like a blind alley to me.

2. By extension, a situation in which no more progress or advancement is possible. After spending years trying to prove his hypothesis but failing to get the results he had hoped for, the physicist feared that he had wasted too much time heading down a blind alley. I'm afraid we've come to a blind alley in our investigation. I'm nervous they're going to cut my funding because my research is at a blind alley—every experiment I've tried so far has failed.

blind alley

A dead end; a position without hope of progress or success. For example, That line of questioning led the attorney up yet another blind alley. This term alludes to a street or alley that has no outlet at one end. [Mid-1800s]

blind alley, (up) a

A dead end, either literally (a street or passage with only one entrance) or figuratively (a situation without hope of progress). The term dates from the sixteenth century.