(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"
a serve that strikes the net before falling into the receiver's court; the ball must be served again
leave unchanged; "let it be"
actively cause something to happen; "I let it be known that I was not interested"
make it possible through a specific action or lack of action for something to happen; "This permits the water to rush in"; "This sealed door won't allow the water come into the basement"; "This will permit the rain to run off"