What does alley mean?
The definition of alley
Al”ley, n.; pl. Alleys.
Etym: [OE. aley, alley, OF. alée, F. allée, a going, passage, fr. OE. aler, F. aller, to go; of uncertain origin: cf. Prov. anar, It. andare, Sp. andar.]

1 A narrow passage; especially a walk or passage in a garden or park, bordered by rows of trees or bushes; a bordered way. I know each lane and every alley green. Milton.
2 A narrow passage or way in a city, as distinct from a public street. Gay.
3 A passageway between rows of pews in a church.
4 (Persp.)
Any passage having the entrance represented as wider than the exit, so as to give the appearance of length.
5 The space between two rows of compositors’ stands in a printing office.

Al”ley, n.; pl. Alleys.
Etym: [A contraction of alabaster, of which it was originally made.]

A choice taw or marble. Dickens.