blind alley vs course of action

blind alley and course of action both are nouns.

Word	Noun	Adjective	Verb	Adverb
blind alley	Yes	No	No	No
course of action	Yes	No	No	No

As nouns, course of action is a hypernym of blind alley; that is, course of action is a word with a broader meaning than blind alley:

blind alley: (figurative) a course of action that is unproductive and offers no hope of improvement
course of action: a mode of action

Other hypernyms of blind alley include course.

blind alley (noun)	course of action (noun)
(figurative) a course of action that is unproductive and offers no hope of improvement	a mode of action
a street with only one way in or out