a narrow street with walls on both sides
"The children played tag in the narrow alley where tall brick walls lined both sides."
a lane down which a bowling ball is rolled toward pins
"She stepped up to the alley and aimed her bowling ball at the pins."
A narrow street or passageway, especially one through the middle of a block giving access to the rear of lots or buildings.
"The child carefully tapped his alley against her stack of marbles in the darkened basement."
A glass marble or taw.
In plain English: An alley is a narrow passage between buildings that isn't meant for regular traffic.
"The baseball player hit the ball into the alley for an easy out."
Usage: An alley is typically found between city blocks and provides direct access to the backyards or service entrances of nearby properties. Do not confuse it with an avenue, which usually runs north-south across wider sections of a town.
A surname.
"The famous director John Alley appeared at the premiere wearing his traditional black suit."
The word alley comes from the French verb meaning "to go." It originally referred to a place where one could walk or pass through.