skittle alley vs alley

skittle alley and alley both are nouns.

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

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

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

Other synonyms of skittle alley include bowling alley.

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