alley vs skittle alley

alley and skittle alley both are nouns.

Word	Noun	Adjective	Verb	Adverb
alley	Yes	No	No	No
skittle alley	Yes	No	No	No

As nouns, alley and skittle alley are synonyms defined as:

alley and skittle alley: a lane down which a bowling ball is rolled toward pins

Other synonyms of alley include bowling alley.

alley (noun)	skittle alley (noun)
a narrow street with walls on both sides	a lane down which a bowling ball is rolled toward pins
a lane down which a bowling ball is rolled toward pins