Used other than figuratively or idiomatically: see blind, alley. A street or passageway that leads nowhere.
A course of inquiry that leads nowhere.
A blind alley or dead end street.
An impasse.
A sack-like cavity, a tube open at one end only.
A circular area at the end of a dead end street to allow cars to turn around, designed so children can play on the street, with little or no through-traffic.